This study evaluated recent changes in the annual incidence of childhood type 2 diabetes in the Tokyo metropolitan area. From 1974 to 2004, a total of 236 students were diagnosed as having type 2 diabetes by the urine glucose screening program at school. The overall incidence of type 2 diabetes was 2.55/100,000. Overall, 83.9% of students with diabetes were obese; junior high school students had a significantly higher incidence than primary school students (0.75 vs. 6.27/100,000). The annual incidences over the 5-yr periods from 1974-2004 were 1.73, 3.23, 3.05, 2.90, 2.70 and 1.41/100,000, respectively. The incidences in 1974-1980 and 2001-2004 were significantly lower than those in 1981-1985, 1986-1990 and 1991-1995, because primary school students in 1974-1980 had a significantly lower incidence (0.27/100,000), and junior high school students in 2001-2004 had a somewhat lower incidence (3.66/100,000) than during 1981-2000. In recent years, Japanese children's lifestyle and eating habits have gradually improved, and this may have contributed to the trend toward decrease in the incidence of type 2 diabetes in 2001-2004 in the Tokyo metropolitan area.