A case-control study determined the association of urinary tract infection (UTI) with genital hygiene practices and sexual activity in pregnant women attending prenatal clinics in Babol, Islamic Republic of Iran. A sample of 100 pregnant women with positive urine cultures (cases) were compared with 150 healthy pregnant women matched for age, social, economic and education status and parity (controls). Escherichia coli was the infecting organism in 83% of cases. Factors associated with UTI included sexual intercourse > or = 3 times per week (OR = 5.62), recent UTI (OR = 3.27), not washing genitals precoitus (OR = 2.16), not washing genitals postcoitus (OR = 2.89), not voiding urine postcoitus (OR = 8.62) and washing genitals from back to front (OR = 2.96).