The purpose of this study was to compare the urinary fluoride levels in subtropical Jamaica just before the beginning of salt fluoridation (250 mg/kg salt) in 1987 and again 20 months later. Four age groups were studied in three locations with low to intermediate fluoride concentrations in the drinking water. The averages of supervised, timed morning fluoride excretions ranged between 12.1 and 27.9 micrograms/h prior to fluoridation as compared with 23.7-67.4 micrograms/h 20 months after the beginning of the sale of fluoridated salt. The fluoride excretions obtained from 24-hour collections ranged from 169 to 485 micrograms/24 h in 1987 and increased to 304-657 micrograms/24 h in 1989. In 1987, the morning fluoride excretions approximated those of French and Swiss children who had a low fluoride intake, but the fluoride levels of 1989 were similar to the data obtained from children who had an intake of 1.2-1.7 mg F/day or consumed fluoridated water.