Introduction: Women become more susceptible to asymptomatic bacteriuria and its complications when they get pregnant due to a combination of hormonal, physiological and mechanical changes. Severe materno-foetal consequences follow untreated infections. The opportunity to avoid these sequelae with treatment, justifies screening, preferably by urine culture, of pregnant women especially those at risk. Objective: The study is aimed at determining the prevalence, associated risk factors and the pattern of organisms responsible for asymptomatic bacteriuria. Methodology: This is a cross-sectional study, conducted at the Obstetrics and Gynaecology department of the University of Benin Teaching Hospital (UBTH) Benin City, between April and July 2009. Pregnant women between the 12th and 36th week gestation age attending their first antenatal clinic formed the study group while premenopausal non-pregnant women (aged 15- 45yrs) were the control group. After collection of demographic and medical data, 10-15ml of clean catch midstream urine samples were collected and cultured. Women whose first urine culture was positive for bacteriuria produced a second sample for repeat culture.