diff --git a/update_attempter.h b/update_attempter.h
index 41b7f8e..2ec6174 100644
--- a/update_attempter.h
+++ b/update_attempter.h
@@ -160,7 +160,7 @@
   BootControlInterface::Slot GetRollbackSlot() const;
 
   // Initiates a reboot if the current state is
-  // UPDATED_NEED_REBOOT. Returns true on sucess, false otherwise.
+  // UPDATED_NEED_REBOOT. Returns true on success, false otherwise.
   bool RebootIfNeeded();
 
   // DownloadActionDelegate methods:
@@ -198,7 +198,7 @@
   virtual bool GetBootTimeAtUpdate(base::Time *out_boot_time);
 
   // Returns a version OS version that was being used before the last reboot,
-  // and if that reboot happended to be into an update (current version).
+  // and if that reboot happened to be into an update (current version).
   // This will return an empty string otherwise.
   std::string const& GetPrevVersion() const { return prev_version_; }
 
@@ -332,7 +332,7 @@
 
   // Helper method of Update() to calculate the update-related parameters
   // from various sources and set the appropriate state. Please refer to
-  // Update() method for the meaning of the parametes.
+  // Update() method for the meaning of the parameters.
   bool CalculateUpdateParams(const std::string& app_version,
                              const std::string& omaha_url,
                              const std::string& target_channel,