The study was conducted to evaluate the effective USAge of working time among health center workers in 4 districts in the East Java Province, i.e. Tuban, Tulungagung, Jombang and Probolinggo. Data was collected by observation (time and motion study) and self reporting (self assessment). The result showed that the effective USAge of working time was vary from health center to health center. The variation of effective USAge of working time according to the observation and the self reporting was from 53.7 to 85.1% and 55.5 to 72.0% respectively. The effective USAge of working time from observation was always less than its from self reporting except in Probolinggo. The Health Center workers in Tuban, Tulungagung and Jombang tended to over-claimed the effective USAge of working time, while the workers in Probolinggo tended to under-claimed it. Percentage of 'over' and 'under-claimed' could be used as 'a correction factor of the self reporting in the future if influence factors of the performance of the health center worker was stable. The performance of health center workers in Probolinggo was better than it was in the other three districts (Tuban, Tulungagung and Jombang).