OBJECTIVE: To determine the risk factors for placenta praevia presenting with severe vaginal bleeding in Mulago hospital, Kampala, Uganda. DESIGN: A case control study. SETTING: Mulago hospital labour suite PARTICIPANTS: Between 15th November 2001 and 30th November 2002 we identified and recruited thirty six parturients with placenta previa who developed severe bleeding and 180 women with normal delivery. The risk factors were studied. VARIABLES OF INTEREST: Socio demographic characteristics, social and family history, gynaecological operations, blood transfusion, medical conditions, past and present obstetric performance and HIV status. RESULTS: Significant predictors for severe bleeding in parturients with placenta praevia were: previous history of evacuation of the uterus or dilation and curettage (O.R. 3.6, CI: 1.1-12.5), delivery by caesarean section in previous pregnancy (O.R. 19.9, CI: 6.4-61.7), residing more than ten kilometres from Mulago hospital (O.R. 2.4, CI: 1.0-5.7) and recurrent vaginal bleeding during the current pregnancy (O.R. 7.3, CI 2.4-63.7). CONCLUSION: Severe bleeding in placenta praevia is associated with high maternal morbidity and mortality. The determinants of severe bleeding in placenta praevia can be used in the antenatal period to identify mothers at risk. These, with prompt interventions to deliver the women can be used to reduce the maternal morbidity associated with this condition.