The present paper reports clinical and pharmacological studies with amoxycillin in the treatment of urinary tract infection. 35 elderly hospitalised patients were treated. Their altered general condition due to underlying diseases explains our moderate success rate (45, 7%). The oral dosage ranged from 1, 5–2, 25 g daily. A maximum serum level of ± 6 μg/ml was observed 2 h after oral administration of 750 mg. This level was ± 4, 5 μg/ml 4 h after oral administration of 500 mg amoxyc