An investigation was carried out upon 431 cases of treated foals to determine the occurrence of disease and mortality in the pre-, peri- and postnatal stage. All cases happened between september 1992 and november 1995 among the clients of a horse practice in northern Germany. From 28 registered cases of prenatal foaldisease 27 foals were lost (96%). 13 mares aborted and only in one case the infectious agent (equine herpesvirus I) was succesfully isolated. Other causes of foal deaths were twin pregnancies (n= 4), and malformations (n= 9). From two cases of torsions of the uterus in the pregnant mare only one was cured and produced a surviving foal. In the perinatal stage 66 foals were treated, but 17 without success (26%). Infectious causes seen in 6 cases lead to death in 5 animals. In the large group of noninfectious causes that affected 51 animals, 7 foals couldn´t be saved. Of a total of 5 mares that had problems giving birth, only one foal managed to survive.Three animals showed inguinal hernias or edemas of the prepuce and in one case no cause of death was found. Among 337 foals presented in the postnatal phase, a total of 42 animals were destroyed (12%). Disease of the respiratory tract seen in 60 horses caused death in 7 animals. Of the 84 animals with gastrointestinal problems 16 horses couldn´t be saved. Of the various forms of musculoskeletal abnormalities seen in 41 foals only 9 had to be destroyed. Diseases of the umbilicus (n= 66), testes (n= 22), eyes (n= 13) and skin (n=3) caused no foal losses. Injuries and following woundinfections occured in 48 horses and ended fatal in 10 cases. The prevention of foal diseases and foal losses is discussed based on the established data of this study.