A total of 387 healthy full term infants who received BCG vaccination at birth were evaluated by the tuberculin PPD test at 6-8 weeks post vaccination. A total of 92% of these infants had visible BCG scars at that time. All infants were tested with PPD but only 264 returned for the test to be read. The tuberculin test was negative in 37 (14%) and of less than 5 mm induration in another 60 (23%) of the infants. The same pattern was observed in different nationalities. Of 11 infants with no BCG scar after vaccination, 3 had positive PPD reactions of more than 5 mm induration. There was a significant correlation between the size of the BCG scar and induration of tuberculin test P less than 0.001. The complications of the vaccination were minimal. We have observed 3 sterile abscesses at the site of BCG vaccination which resolved spontaneously. We think the available vaccine is safe and potent, and that the rate of BCG scar formation and of tuberculin conversion is higher than in most studies.