Frequency of elementary and reticular chlamydial bodies was investigated by direct immunofluorescence tests in ejaculates collected from 52 men, 60 stallions, 42 bulls, and 66 boars using the kits of Progen Biotechnic GmbH and the microscope Labophot-2 Nikon. At the same time, qualitative semen tests, including ejaculate volume, sperm motility, percentage of live and dead sperms and morphological' analyses (Vĕzník and Svecová, 1992) were done. Repeatability of the findings was checked in a group of nine bulls housed at the institute and sampled at weekly intervals for 3 to 4 months (Tab. 1). Chlamydiae were demonstrated in 3.8%, 14.3%, 3.4% and 9.1% of the human, bull, stallion and boar ejaculates, respectively (Fig. 1). A relation between the presence of Chlamydiac and impaired functional and morphological quality of ejaculates was found in contaminated human (only two samples) and bull ejaculates (Fig. 2) and in one of the two positive stallion ejaculates (Tab. II, Fig. 3). Direct tests for Chlamydiae should be included into semen health and quality checks as one of the major tasks of assisted reproduction in human and veterinary medicine.