Vaginal/cervical swabs, catheter urine and/or puncture of the bladder (p.b.) from 880 females with urogenital diseases were examined microbiologically. Mycoplasmas (Ureaplasma urealyticum, Mycoplasma hominis) could be isolated from 321 females (36.5%), and Chlamydia trachomatis from 42 (4.8%). Mycoplasmas and C. trachomatis were more frequent in the age between 21 and 30 years (53 and 11.8% respectively). In 32.8% of the entire collective mycoplasmas could be detected in vaginal swabs. In contrast only 23.2% of the patients from whom catheter urine or p.b. was collected showed mycoplasmas. Of 880 females 117 (13.3%) had mycoplasmas in vaginal smear material, and 172 (19.5%) showed mycoplasmas in the vaginal swab as well as in catheter urine or p.b. From 32 (3.6%) females mycoplasmas could be detected only in catheter urine or p.b. Of 410 males mycoplasmas were isolated from urethral, catheter urine/p.b. and/or from ejaculate in 26.3%. Most frequently, positive carriers were in the age between 31 and 40 years (38.1%). C. trachomatis was found in 22 patients (5.4%). The frequency of mycoplasmas in urethral smear was 24.9%, in catheter urine/p.b. 13.6% and in ejaculate 15.6%. In 50 (12.2%) patients mycoplasmas were isolated both from urethral and catheter urine/p.b., in 52 (12.7%) only from urethral smear and in 6 (1.4%) only from catheter urine/p.b. Two species of mycoplasmas could be detected in this non-quantitative study: U. urealyticum which was isolated more frequently, and M. hominis.