diff --git a/src/main/java/org/altbeacon/beacon/service/BeaconService.java b/src/main/java/org/altbeacon/beacon/service/BeaconService.java
index 3a50855a7..29f0d9007 100644
--- a/src/main/java/org/altbeacon/beacon/service/BeaconService.java
+++ b/src/main/java/org/altbeacon/beacon/service/BeaconService.java
@@ -37,8 +37,10 @@
 import android.os.Build;
 import android.os.Handler;
 import android.os.IBinder;
+import android.os.Looper;
 import android.os.Message;
 import android.os.Messenger;
+import android.support.annotation.MainThread;
 import android.support.annotation.NonNull;
 
 import org.altbeacon.beacon.Beacon;
@@ -145,9 +147,16 @@ static class IncomingHandler extends Handler {
         private final WeakReference<BeaconService> mService;
 
         IncomingHandler(BeaconService service) {
+            /*
+             * Explicitly state this uses the main thread. Without this we defer to where the
+             * service instance is initialized/created; which is usually the main thread anyways.
+             * But by being explicit we document our code design expectations for where things run.
+             */
+            super(Looper.getMainLooper());
             mService = new WeakReference<BeaconService>(service);
         }
 
+        @MainThread
         @Override
         public void handleMessage(Message msg) {
             BeaconService service = mService.get();
@@ -206,7 +215,7 @@ else if (msg.what == MSG_SYNC_SETTINGS) {
      */
     final Messenger mMessenger = new Messenger(new IncomingHandler(this));
 
-
+    @MainThread
     @Override
     public void onCreate() {
         bluetoothCrashResolver = new BluetoothCrashResolver(this);
@@ -294,6 +303,7 @@ public boolean onUnbind(Intent intent) {
         return false;
     }
 
+    @MainThread
     @Override
     public void onDestroy() {
         LogManager.e(TAG, "onDestroy()");
@@ -330,6 +340,7 @@ private PendingIntent getRestartIntent() {
     /**
      * methods for clients
      */
+    @MainThread
     public void startRangingBeaconsInRegion(Region region, Callback callback) {
         synchronized (rangedRegionState) {
             if (rangedRegionState.containsKey(region)) {
@@ -342,6 +353,7 @@ public void startRangingBeaconsInRegion(Region region, Callback callback) {
         mCycledScanner.start();
     }
 
+    @MainThread
     public void stopRangingBeaconsInRegion(Region region) {
         int rangedRegionCount;
         synchronized (rangedRegionState) {
@@ -355,6 +367,7 @@ public void stopRangingBeaconsInRegion(Region region) {
         }
     }
 
+    @MainThread
     public void startMonitoringBeaconsInRegion(Region region, Callback callback) {
         LogManager.d(TAG, "startMonitoring called");
         monitoringStatus.addRegion(region, callback);
@@ -362,6 +375,7 @@ public void startMonitoringBeaconsInRegion(Region region, Callback callback) {
         mCycledScanner.start();
     }
 
+    @MainThread
     public void stopMonitoringBeaconsInRegion(Region region) {
         LogManager.d(TAG, "stopMonitoring called");
         monitoringStatus.removeRegion(region);
@@ -371,6 +385,7 @@ public void stopMonitoringBeaconsInRegion(Region region) {
         }
     }
 
+    @MainThread
     public void setScanPeriods(long scanPeriod, long betweenScanPeriod, boolean backgroundFlag) {
         mCycledScanner.setScanPeriods(scanPeriod, betweenScanPeriod, backgroundFlag);
     }
diff --git a/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScanner.java b/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScanner.java
index 4c640cd6f..a176da53d 100644
--- a/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScanner.java
+++ b/src/main/java/org/altbeacon/beacon/service/scanner/CycledLeScanner.java
@@ -1,7 +1,6 @@
 package org.altbeacon.beacon.service.scanner;
 
 import android.Manifest;
-import android.annotation.SuppressLint;
 import android.annotation.TargetApi;
 import android.app.AlarmManager;
 import android.app.PendingIntent;
@@ -125,6 +124,7 @@ public static CycledLeScanner createScanner(Context context, long scanPeriod, lo
      * between LOW_POWER_MODE vs. LOW_LATENCY_MODE
      * @param backgroundFlag
      */
+    @MainThread
     public void setScanPeriods(long scanPeriod, long betweenScanPeriod, boolean backgroundFlag) {
         LogManager.d(TAG, "Set scan periods called with %s, %s Background mode must have changed.",
                 scanPeriod, betweenScanPeriod);
@@ -165,6 +165,7 @@ public void setScanPeriods(long scanPeriod, long betweenScanPeriod, boolean back
         }
     }
 
+    @MainThread
     public void start() {
         LogManager.d(TAG, "start called");
         mScanningEnabled = true;
@@ -175,7 +176,7 @@ public void start() {
         }
     }
 
-    @SuppressLint("NewApi")
+    @MainThread
     public void stop() {
         LogManager.d(TAG, "stop called");
         mScanningEnabled = false;
@@ -194,6 +195,7 @@ public void setDistinctPacketsDetectedPerScan(boolean detected) {
         mDistinctPacketsDetectedPerScan = detected;
     }
 
+    @MainThread
     public void destroy() {
         LogManager.d(TAG, "Destroying");
         // We cannot quit the thread used by the handler until queued Runnables have been processed,
@@ -218,7 +220,7 @@ public void run() {
 
     protected abstract void startScan();
 
-    @SuppressLint("NewApi")
+    @MainThread
     protected void scanLeDevice(final Boolean enable) {
         try {
             mScanCyclerStarted = true;
@@ -285,6 +287,7 @@ protected void scanLeDevice(final Boolean enable) {
         }
     }
 
+    @MainThread
     protected void scheduleScanCycleStop() {
         // Stops scanning after a pre-defined scan period.
         long millisecondsUntilStop = mScanCycleStopTime - SystemClock.elapsedRealtime();
@@ -308,6 +311,7 @@ public void run() {
 
     protected abstract void finishScan();
 
+    @MainThread
     private void finishScanCycle() {
         LogManager.d(TAG, "Done with scan cycle");
         try {