HIV/AIDS model for sexual transmission with explicit incubation period is proposed as a system of discrete time delay differential equations. The threshold and equilibrium for the model are determined and stabilities are examined. Qualitative analysis of the model is also presented. We use the model to study the effects of public health educational campaigns on the spread of HIV/AIDS as a single-strategy approach in HIV prevention. The education-induced basic reproductive (RE) for the model is compared with the basic reproductive number (R0) for the HIV/AIDS in the absence of any intervention to assess the possible community benefits of public health educational campaigns. We conclude from the study that in settings where public health educational campaigns of HIV/AIDS are effective and with reasonable average numbers of HIV-infected partners, public health educational campaigns can slow down the epidemic and are more effective when given to both sexually immature (pre- and early adolescence) and sexually mature individuals (adults) concurrently. © 2008 Elsevier Inc. All rights reserved.