The forkhead box O1 (FoxO1), the first discovered member of the FoxO family, is a critical transcription factor predominantly found in insulin-secreting and insulin-sensitive tissues. In the pancreas of adults, FoxO1 expression is restricted to islet β cells. We determined that in human islet microarray datasets, FoxO1 expression is higher than other FoxO transcription factors. Our analyses of three human islet datasets revealed that FoxO1 expression tends to shows a negative correlation with type 2 diabetes and no correlation with body mass index (BMI) between individuals with low levels of HbA