Search for Trichomonas vaginalis was carried out in direct (in 0.85% NaCl and 0.1% safranine) and fixed stained microscopical preparations ( Wright or Giemsa methods, after fixation with 70% methyl alcohol) and cultures ( Pavlova, Johanson-Trussel-John, Roiron-Ratner, Simic media), from materials of the vagina, urethra and cervix uteri. In the years 1955-1999 a total of about 12000 women were examined. The prevalence of T. vaginalis in women population of Lódź region was high (from 26.6% still 78.0%); on the last ten years in about half of the sample examined women were infected of T. vaginalis.