The theory of planned behaviour (TPB) provides a conceptual model for understanding individual cognitions that influence behavioural intentions and enactment of the actual behaviours. This study examined the applicability of the TPB and the additional predictive role of perceived risk in predicting intended use of voluntary HIV counselling and testing (VCT) services. We conducted a cross-sectional questionnaire survey among 918 primary school teachers in the Mwanza region, Tanzania between September 2003 and November 2003. Analysis was based on 737 teachers (mean age 38.9) who had never tested for HIV. Results of the hierarchical regression analysis indicate that perceived behavioural control and attitude toward using VCT services were significant predictors of intention to use VCT services in the TPB model. Perceived behavioural control added 12% of variance to intention over and above attitudes and subjective norms, while perceived risk added 3% of variance. Socio-economic status did not moderate the predictive value of the TPB components. The present study demonstrates that the TPB is a useful conceptual framework for predicting intended use of HIV counselling and testing services among Tanzanian teachers. A theory-based VCT intervention programme among Tanzanian teachers should mainly focus on reducing social and psychological barriers related to the use of VCT services.