Adherence to cultural values especially with regard to sexual fidelity is very important in the spread of HIV infection. Moreover, to the extent that there is no known cure or vaccine for AIDS, behaviour change constitutes the most effective way to stop the spread of the epidemic. Therefore, anthropologists and other social scientists need to be conversant with the social and cultural context in which sex is undertaken and the attendant risk thereof. Hence, it is important to undertake detailed ethnographic analyses in different cultural settings that can inform policy and programs aimed at HIV/AIDS prevention. This paper presents data on cultural attitudes, values and norms regarding sexual behaviour in general and fidelity in particular among the Batooro who inhabit the Kingdom of Tooro, Western Uganda. Data presented in this paper shows that when infidelity takes place among married Batooro, it is unusual for a woman to leave her husband because of the man’s infidelity. The woman may quarrel, but she will not leave her husband. On the other hand, data presented show that infidelity can lead a man to leave his wife. All this reflects a cultural value in many Ugandan Communities that put a premium on a wife’s docility and fidelity, while accepting, or even expecting a man to have more than one sexual partner. This needs to be taken into account by HIV/AIDS control programmes.