Despite widespread use of sentinel surveillance systems in monitoring the magnitude of HIV-1 infection in populations, little is known of how the trends they produce compare with those of the larger populations which they support to represent. The objective of this study, therefore, was to assess how useful sentinel surveillance data on HIV-1 infection might be in estimating the magnitude of HIV-1 infection in the general population. To achieve this, results from a population based study on HIV-1 infection in Bukoba town were compared with those from antenatal mothers and blood donors, all from the same town. The studies were done during the period of 1987-90. The overall HIV-1 prevalence was highest in the general population sample at 24.2% (95% CI 20.6-27.8) followed by that in antenatal mothers at 22.4% (95% CI 20.6-25.2) and lowest in blood donors at 11.9% (95% CI 9.1-15.3). Seroprevalence among antenatal clinic attenders was significantly lower than that of females from the general population sample (p = 0.016). Prevalence among female blood donors did not differ significantly from that of females from the general population sample (p = 0.06). Blood donor males had a lower HIV-1 seroprevalence when compared to that from the general population males (p = 0.038). The age group 25-34 years had the highest prevalence of HIV-1 infection in all the three populations indicating that this group is at the highest risk of HIV infection and that the three populations show a similar trend of age specific prevalence. From these findings, it is noted that female blood donors as a sentinel population represents more closely estimates of HIV-1 seroprevalence of females in the general population than antenatal clinic attenders or male blood donors. Further studies are proposed in different settings in order to come up with guidelines on the methodology of using sentinel surveillance populations in monitoring HIV-1 infection.