Bacteriuria of pregnancy is a common condition which is thought to be associated with serious sequelae in mother and fetus. A programme of screening, treatment and follow-up is likely to be cost-effective, but will depend on local prevalences of bacteriuria and pyelonephritis. If treatment is undertaken, nitrofurantoin and cephalexin are both safe and effective and have resistance rates of below 10%. Amoxycillin is also safe, but resistance rates in Escherichia coli are about 40%. A 7 day course of treatment remains advisable.