The aim of the study was a quantitative and qualitative analysis of microflora, presentation of current data about prevalence of the microflora on the skin and mucous membranes, and determination of its possible effect on reproduction of English full blood horses bred in Poland. The material for analyses was sampled from the skin and mucous membranes (385 samples) of 55 English full blood mares. Taking into account reproduction traits, the mares were classified into three groups. Six yeast-like species, including five species from the genus Candida (C. albicans, C. guiliermondii, C. lusitaniae, C. sp., and C. tropicalis) and Trichomonascus ciferrii, were detected on the skin and mucous membranes in the English full blood mares. Growth of yeasts was observed in more than half of the samples taken from mares that had foaled and approximately 46 % of non-conceiving and barren mares. The high prevalence of various yeast strains in the mouth, nostrils, and collateral groove may suggest widespread occurrence of the microflora in the breeding environment. The results obtained indicate that the yeasts isolated in this study may be components of the normal microflora of the skin and mucous membranes in horses. The analysis results do not indicate unambiguously that the isolated microflora affects reproduction in mares, although this cannot be excluded.