Clinical diagnosis can often indicate whether the patient has an infection of the lower or the upper urinary tract. The symptoms may be misleading, however. Examination of the urine is therefore essential. Recommendations are made for sampling, microscopy, stix-tests and interpretation of cultures. Species distribution and sensitivity patterns are presented. There has been a trend towards increasing antimicrobial resistance during the period 1982 to 1990. The recommended drugs for uncomplicated infections of the lower urinary tract in women include nitrofurantoin, amoxicillin, pivampicillin, pivmecillinam, sulfamethizole, trimethoprim and co-trimoxazole, with a possible preference for trimethoprim and nitrofurantoin (should be used with caution in elderly patients). Duration of therapy is normally three days. In pregnant women and in men with an infection of the lower urinary tract the duration of treatment should be 7-10 days. Specific drugs are recommended for these groups of patients. Drugs recommended for infection of the upper urinary tract and complicated infections of the lower urinary tract include amoxicillin, ampicillin, ciprofloxacin/ofloxacin, co-trimoxazole, pivampicillin and pivmecillinam. Duration of treatment should be 7-10 days. Treatment is also recommended for reinfection, for children, for patients with asymptomatic bacteriuria and for patients with permanent bladder catheters. Long-term prophylaxis and general advice on lifestyle are also discussed.