The heavy losses of reindeer calves in the Angeså forest herd and their seasonal occurrence are discussed on basis of the results obtained from the tables. The management, productivity and breeding conditions of this herd are estimated to be, for the most part the same as in other forest herds. The calf losses in the Angeså herd are high, during some years very high, while the reproductivity rate is comparable to that of the caribou. The extensive form of management makes it impossible to clarify most of the causes for the losses and their interrelationships. Preobrazhenskii (1961) emphasizes the importance of an intensive form of management and of counting the herd at least four times annually in order to control and prevent different kinds of losses. Skjenneberg & Slagsvold (1968) point out that the extensive form of management hinders progress in reindeer breeding, especially in the areas of selection and disease control. These statements seem to be highly relevant to Swedish reindeer breeding as well. The results from the tables clearly indicate the high total losses, the high losses during certain summers and the importance of accessible winter fodder for calf production and post-natal survival. It is important to investigate whether supplementary feeding with commercially available fodder, hay, and minerals would result in better economy in reindeer breeding. It is also desirable to investigate improved methods for supplementary feeding. During certain years calf losses are very high during the summer, but the relationships between different causes (such as stress, bloodsucking diphtera, parasites, keratitis etc.) are not clear. Surveillance of the animals during the calving season, marking of the calves before the fly season and summer heat, and developing a higher degree of domestication will probably result in smaller losses during spring and summer. If the practice of marking the calves in summer is to be continued, steps must be taken to protect the health of the animals. Such steps include making available sun shades, smoke fires against bloodsucking insects, running water, and salt and mineral feedings. Due to the extensive management form, it has not been possible to determine the extent of the real winter losses. For similar reasons the extent of the losses caused by parasites remains unclear. A continuous pathological examination of dead animals seems to offer the only possible method for clarifying the causal connections of the losses. As a consequence of the extensive form of management, the carcasses of animals that die during spring and summer are destroyed by heat and scavengers. One way of obtaining material useful for pathological examination would be a telemetric method, in which a radio signal is transmitted when the animals is dead or dying (Moell & Rehbinder 1975).