Data on the prevalence of the first ejaculating emission for 83,902 Chinese boys 9 through 18 years were collected using interviews. Median spermarcheal ages (MSAs) were calculated by using the status quo data and probit analysis. Subjects consisted of 61,812 Han boys from urban and rural areas in 29 provinces, and 22,090 minority boys from 17 minority ethnic groups. Median spermarcheal ages were 14.24 years for urban Han boys and 14.85 years for rural Han boys, and ranged from 13.46 to 16.32 years for the 17 minority ethnic groups. The differences in MSAs between urban and rural Han boys in each province were significant and the correlation between MSA of urban and rural boys in each province was high (r = 0.83, P < 0.001). For both urban and rural Han boys, there were significant geographic variations. MSAs of boys living in north China were generally higher than those living in the south, while those living in the west were higher than those living in the east. Variation in MSA may be related to ecological conditions in the Chinese Han populations. The different estimates of spermarcheal ages with two approaches, periodical urine sample analysis vs. interview, and their effect on estimating male puberty are discussed. Am. J. Hum. Biol. 12:577–587, 2000. © 2000 Wiley-Liss, Inc.