Botswana, with its estimated HIV prevalence of 37%, instituted a policy of universal access to antiretroviral therapy (ART) in 2002. Initial enrolment lagged behind expectations, with a shortfall in voluntary testing that observers have attributed to HIV-related stigma - although there are no published data on stigma among HIV-positive individuals in Botswana. We interviewed 112 patients receiving ART in 2000, finding evidence of pervasive stigma in patterns of disclosure, social sequelae, and delays in HIV testing. Ninety-four percent of patients reported keeping their HIV status secret from their community, while 69% withheld this information even from their family. Twenty-seven percent of patients said that they feared loss of employment as a result of their HIV status. Forty percent of patients reported that they delayed getting tested for HIV; of these, 51% cited fear of a positive test result as the primary reason for delay in seeking treatment, which was often due to HIV-related stigma. These findings suggest that success of large-scale national ART programmes will require initiatives targeting stigma and its social, economic and political correlates.