The number of newly registered cases of tuberculosis has been increasing in the age group 15-19 year-old and over. To investigate the prevention of tuberculosis among young people under 20 years old, a survey was conducted on reported cases of tuberculosis among Osaka Prefectural high school students during the period from April, 1989 to May, 1994. Altogether 67 cases were reported from their schools during this period. Although there was a decrease in the total number of students since 1990, there was no corresponding decrease in the number of cases of tuberculosis. Of the total number of cases among high school students registered at public health centers in Osaka, only 23% were reported from the high schools. Cases confirmed bacteriologically positive consisted 13% of all cases. Male students accounted for 61% of reported cases. The methods of detection included medical consultation due to symptoms (75%), mass radiography (18%) and pre-employment health checkup (7%). 46% of cases reported during the first school year were discovered by mass radiography. While 24% of all cases were detected in April, no less than 46% of cases among those in the first school year were detected in April. Compared with those detected in any other school years, cases detected in the first school year showed some characteristic differences with regards to detection and bacteriological results. There has been one tuberculosis epidemic which accounted for six cases during the past five years.(ABSTRACT TRUNCATED AT 250 WORDS)