The efficacy of pivmecillinam for empirical treatment of acute uncomplicated urinary tract infection (UTI) was initially reported in clinical trials published in the 1970s and 1980s. Bacteriological cure rates observed in these trials were consistently >85%, and studies of different dosing regimens suggested that a 3 day course was appropriate. Comparative studies reported that pivmecillinam was equivalent to other antimicrobial agents in terms of clinical and bacteriological outcomes. These studies also documented that pivmecillinam was effective for treatment of Staphylococcus saprophyticus infections, was acceptable for use in pregnancy and was well tolerated. Subsequent widespread use of pivmecillinam in Scandinavian countries has led to a body of clinical experience which confirms the efficacy and safety of this antimicrobial agent in the treatment of acute cystitis. Recently, two large, prospective, randomized, double-blind, multi-centre clinical trials have been completed to assist in defining the role of this antimicrobial agent in the treatment of acute cystitis. A comparison of 3 day courses of pivmecillinam or norfloxacin, both at 400 mg bd, showed higher bacteriological cure rates with norfloxacin but generally similar clinical outcomes. A second, dose-ranging study found that pivmecillinam, given bd for 7 days, led to superior bacteriological and clinical outcomes at short-term follow-up than the 3 day regimen. Pooling bacteriological outcomes from the two studies showed similar outcomes with 7 days of pivmecillinam 200 mg bd or 3 days of norfloxacin 400 mg bd. The shorter, 3 day, course achieved similar short-term clinical outcomes to 7 days of pivmecillinam and 3 days of norfloxacin in women aged < or =50 years. These recent studies confirm earlier reports and clinical experience that pivmecillinam is effective and well tolerated for the treatment of acute cystitis in women.