An observational study was initiated to provide general information on calf health and estimates of frequency and of economic impact of calf diseases in farms with extensive beef production. The study was planned as a cohort study and included all calves born during the calving season of 1993/94 in 105 cow-calf farms in western Switzerland. The total preweaning mortality was 8.5% (123 calves out of 1452 calvings); 2.5% of the calves were stillborn, and 6.0% died or were euthanized before weaning. Forty-four percent of all losses were recorded in the perinatal period (i.e. the first 48 hours p. p.). The average preweaning mortality among liveborn calves at farm level was 6.1%. A large variation in mortality was observed from farm to farm (0-50%). In 50% of the post mortem analyses, respiratory disease was diagnosed as the cause of death. Twenty-two percent of all calves were treated at least once by a veterinarian. Thirty-six percent of all treatments were performed because of diarrhea, 26% because of respiratory disease and 15% because of umbilical problems. From birth to weaning age, the average treatment costs including calving assistance, medication and prophylactic measures were SFr, 23.80 per calf.