AbstractTanzania like other Sub Saharan African countries is having high HIV prevalence. Adolescents are among the risk groups. So far studies focusing on long term survey of primary school pupils HIV/AIDS knowledge, social norms and behavioural factors are lacking in Sub Saharan Africa. ObjectiveAim was to explore the level of communication, access to information about AIDS, social norms, self efficacy and attitude towards becoming sexually active as well as knowledge and behaviour in relation to HIV/AIDS among primary school pupils in 2005 compared to 1992.MethodsA repeated cross sectional quantitative survey was conducted among grade six and seven of 18 primary schools in Kilimanjaro and Arusha regions of Tanzania. Schools were randomly selected. The study was based on the theory of reasoned action. The same instrument and data collection procedures were used in 2005 as it was in 1992. Instrument used was a self administered questionnaire. Ethical clearance was obtained from the Ministry of Health in Tanzania. Pupils voluntarily signed an informed consent form before filling the questionnaire. Data analysis was done using statistical package for social sciences (SPSS) version 12. Chi-square test was used to compare groups, t-test, and one way ANOVA were used to compare means whenever appropriate. Bivariate analysis was done to determine association of variables in relation to AIDS knowledge and sexual behaviour. Results A total of 2026 pupils participated in 1992 and 2069 pupils participated in 2005.Level of communication and information about AIDS had increased in 2005 compared to 1992. Teachers were reported by pupils to be the most frequent people to communicate with pupils about AIDS, and school was the commonest source of AIDS information. While health workers were reported to be the least frequent people to communicate AIDS information to pupils. Girls reported parents to have communicated with them about AIDS more than did boys. There was a general increase in the general level of knowledge in 2005 (Mean 13.56) compared to 1992 Mean 12.03 (P.000). But there was decline in the level of knowledge on condom in 2005 as only 43% knew that condom can prevent HIV infection compared to 62% in 1992. Only 45% pupils in 2005 knew that a person can have HIV but shows no sign. Overall levels of social norms and self efficacy have increased in 2005 compared to 1992. A smaller proportion of pupils were sexually active in 2005 (18.8%) than that of 1992 (31.8%). Conclusion and recommendationsDespite the overall increase in the level of knowledge among primary school pupils. They still lack knowledge on crucial HIV/AIDS related issues that put them at risk of acquiring HIV. Lack of knowledge on condom and that a person can have HIV and shows no sign can lead to unprotected sexual intercourse among the sexually active pupils with dangerous consequences. Further research is needed to know why more than 20 years of HIV epidemic in Tanzania pupils still lack knowledge on life saving issues on HIV/AIDS namely condom and presence of asymptomatic carriers. AIDS education providers should focus on ways of prevention of infection including condom and address misconceptions among school pupils.