A numerical and functional deficit of natural killer T (NKT) cells has been reported to be associated with the pathogenesis of Caucasian patients with type 1 diabetes. However, a conflicting finding of a higher frequency of NKT cells (Valpha24+ Vbeta11+ T cells) was observed in islet-associated Ab+ and Ab- Japanese "classic" type 1 diabetes. Here, we combined the data of NKT cell frequency in Ab+ and Ab- "classic" type 1 diabetic patients and then analyzed the relationship between NKT cell frequency and disease activity.