The present study aimed to detect possible differences in the data of oral squamous cell carcinomas (OSCC) cases diagnosed in a Dental School in São Paulo city over the last 40 years. The records of patients diagnosed as having OSCC between the years 1960 and 2008 were retrieved. The whole period was divided into four time periods. A total of 1,564 cases were reviewed. The variables analyzed were: sex, age, race, anatomical site, lesion duration, and lesion size. The chi-square test was used for statistical analysis. Overall, males were more affected than females (3:1), but when comparing the first and last time periods, the ratio decreased significantly (5.8:1 to 2.8:1). A significant increase in the rate of OSCC in patients over 80 years was observed in the last time periods. The gingiva was the most affected site, but the frequency of lower lip involvement increased in the last time period. Regarding lesion size and duration of symptoms at the time of diagnosis, there was a significant difference between the first and last time periods. Smaller lesions were found and the time of lesion development was shorter in the last few years of the study. These findings support the optimistic view that, in recent years, earlier diagnosis has resulted from early oral cancer detection in São Paulo city. (J Oral Sci 52, 267-273, 2010)