We reviewed diabetes apps for Android smartphones. We compiled a list of free and paid apps in April 2011 by searching the Android Market for apps which could track self-monitoring of blood glucose (SMBG), diabetes medications or calculate prandial insulin dosages. Two reviewers independently evaluated six features per app, using a five-point Likert scale. The sum of the six ratings was the composite usability score, and the mean score of an app's features was the average usability score. Of the 80 Android diabetes apps identified, 42 unique apps were eligible for the study. SMBG recording was present in 36 (86%) of the apps, a tool to track insulin or oral diabetic medications was found in 19 (45%) apps, and a prandial insulin dose calculator existed for 11 (26%) apps. Eighteen apps were free of charge and the other 24 apps had a mean purchase price of $2.86 (range 0.99-6.99). The mean composite usability score was 11.3 out of a possible 30. The mean average usability score was 3.0 out of a possible 5.0. Only four of the 42 apps had a composite usability score above 20 and none offered direct data input from glucometers, suggesting that few provided a comprehensive method of diabetes management. The apps Glucool Diabetes, OnTrack Diabetes, Dbees and Track3 Diabetes Planner were the highest rated. Clinicians may find it useful to recommend these apps.