Human immunodeficiency virus (HIV) infection and the development of the acquired immunodeficiency syndrome (AIDS) are increasing at an alarming rate especially in the sub-Saharan region. Pregnant women susceptible to HIV and its transmission to the fetus provide a unique opportunity for implementing preventive strategy against HIV infection of newborn babies. During the period of August-December 2005 a cross-sectional study was conducted at the Fath-Elrahman Elbashir antenatal clinic, Khartoum Teaching Hospital, to investigate pregnant women's basic knowledge and attitude toward HIV and mother to child transmission as well as voluntary counseling and testing. Pre-tested structured questionnaires were given to antenatal attendants by professional counselors. Their basic socio-demographic and obstetric characteristics were obtained. Respondents' knowledge about HIV and mother to child transmission were tested. In addition, their willingness toward HIV testing was also reported. Out of the 1,005 women investigated, 79% had basic knowledge about HIV. Those who were resident in Khartoum and whose age was > or =26.1 years and their education level was secondary and above were found to be more knowledgeable about HIV. More than half of respondents were aware of mother to child transmission. Older (> or =26.1 years), educated, and working mothers were found to be more knowledgeable about mother to child transmission. Willingness to undergo the test was demonstrated in 72.8% of respondents. However, only 30.3% had the test done. Older women, primigravidae, and Muslims have higher acceptance of voluntary counseling and testing. There is a need to extend the voluntary counseling and testing program in all antenatal clinics. In addition, there is a need to increase the level of education and raise health awareness about HIV and mother to child transmission.