Caribou herd size, herd structure, and recruitment estimates are important for management decisions. In March 2000 an aerialsurvey by helicopter for caribou abundanceand herd structure was completed in Kangerlussuaq – Sisimiut. Flight height was 100metres, flight speed was ≤ 100 kilometre/hour and strip width was 500 metres toeither side of the helicopter. In 1998 and2000, snowmobile ground surveys for herdstructure were also conducted in February-March. Both aerial and ground surveysgave annual recruitment estimates. Mean group size was 2.7 caribou from theaerial herd structure count and averaged3.1 from the two ground counts. Thesegroup sizes are similar to previous findingsand typical for Greenland caribou populations. Caribou density was 2.76 per km2 inthe high-density stratum and 1.19 per km2in the low-density stratum. The formercould be considered a threat to vegetation,and even the latter has previously been considered too high for range recovery. The calfpercentage to the total herd was 26.5%. Thelate winter fertility index and annual recruitment estimate was c. 68 calves per 100female caribou. This high recruitment ratewill promote rapid increase in the population, specifically since there are no predators. The bull to cow ratio was about onebull to every 1.2 cows, and is not unusualcompared with North American herds. Ifnatural mortality is between 4 and 7%, thenon the present herd size between 2,000 and3,600 animals may be expected to dieannually. This study’s estimate for the pre-calving population size of the Kangerlussuaq-Sisimiutcaribou herd in region North in March 2000is c. 51,600 caribou ± 11,200 (90% CI). Therecommended harvest quota for regionNorth was increased to 7,000 caribou for the August-September hunt 2000, and hunters were asked to shoot more females. Therecommendation was increased to 10,000caribou for the 2001 hunt, with the stipulation that half the quota should be allocatedto females only, if further populationgrowth was to be halted. Halting population growth cannot be effectively achievedthrough hunter harvest unless femalesmake up a large proportion of the harvest. The Kangerlussuaq-Sisimiut caribou herd ispresently capable of increasing rapidly innumber. The present estimate for 2000 isapproximately five times the 1996 estimateand larger than any previous estimate forthis herd. In addition, there is the possibilitythat the herd has expanded its range, andsome suggestion of increased natural mortality and animals in poor condition. Increasing the caribou harvest for this region mayavert a possible rapid increase in herd sizeand subsequent range damage.