Obligate embryonic diapause is one of the features within reproduction biology of the roe deer. In the period of the diapausa independently from the pregnancy the corpus luteum (CL) is active, but the hormone production is stabilised at a low level. The quantity of oestradiol and prolactin increases only before and during the implantation. The reactivation of the blastocyst is not a consequence of the change in maternal hormone production (progesterone, oestradiol, prolactin); there is a uterus-specific hormone which is supposed to be responsible for starting the embryo development. In roe deer the well-known luteolysis mechanism does not work, the CL remains from December till January, despite the fact that the doe is pregnant or not, and so the possibility of another rutting season is excluded (strictly mono-oestrous species). In the examined populations the fertility rate occurred high (88-100%), the pregnancy rate is 88-100%. The average number of foetuses (primary natality) 1.67-2.16, average number of born fawns 1.54-2.06 (secondary natality), the reared litter size 0.94-1.55 (tercier natality). The distribution of foetus number: 1 foetus 13.46%, 2 foetuses 73.72,3 and 4 foetuses 5.77%. The distribution of reproductive losses: intrauterinal 2.83-18.0% (primary mortality) and rearing losses 6.01-42.45% (secondary mortality). However, it can be expressed, that the main part of reproductive losses occurs in the rearing period (May-September). The preventive game management and hunting efforts should be concentrated on this period.