The role of Streptococcus agalactiae (group B streptococci, GBS) was investigated for a period of one year in different clinical forms of urinary tract infection in males and non-pregnant females over 14 years of age. The pathogen has been isolated in quantities of greater than or equal to 10(5) cfu/ml in midstream voided urine from 32 patients with clinical signs of urinary tract infection and pathologic urinary sediment. In every group of B isolates the antibiotic sensitivity to antimicrobial agents was determined by the single disk method of Kirby-Bauer. GBS with the same characteristics were established in urethral specimens of 4 males as well as in the vagina and faeces of 11 females. As a rule, peroral treatment with ampicillin proceeded successfully. In addition, women with streptococcal vaginitis were treated topically with 2% solution of chlorhexidine. Our results have demonstrated that GBS might cause urinary tract infection, but the evaluation of GBS isolated in urine specimens is complex.