Sex, age and temporal distribution of 439 Isle Royale [Michigan, USA] moose (Alces alces), dying of natural causes from approximately 1950-1969, are analyzed. At least 45% of the animals examined had been killed by wolves (Canis lupus). Calves and yearlings comprised 29.3% and 3.5%, respectively, of the wolf-kills, but were underrepresented in relation to their occurrence in the population. A pronounced selectivity for old animals was demonstrated with age classes 12-17 yr comprising 29.3% of the wolf-kills. As a group, the wolf-kills also showed a significant preponderance of females. Age distribution of moose dying of unknown causes (34.9% of the total sample) differed significantly from that of wolf-kills. Young adults comprised 24.2% of the unknown mortality remains, while middle-aged (7-11 yr) and old animals accounted for 37.9% and 12.4%. Moose dying of unknown causes showed a highly significant preponderance of males, but age distribution between sexes did not differ statistically. Age distribution among winter wolf-killed moose showed a significant increase of younger animals in the kill during the latter half of the period 1959-69. The role of wolf predation in the regulation of this population is discussed.