In 1995, Harlequin Duck pair surveys were conducted on 329 km of 22 streams finding a minimum of 37 males and 23 females. A sex ratio of 1. 51:1 (m:f, n=600) was observed during 1974-1975 and 198901995 Montana pair surveys. Brood surveys were conducted on 371 km of 23 streams yielding a minimum of 16 females, 40 juveniles, and 2 unknowns. Harlequins were reported on 19 additional streams. Breeding was confirmed for the first time on both the Middle Fork of Rock Creek, Deerlodge National Forest (Ben Canard pers. comm. ) and the West Fork of the Yaak River, Kootenai National Forest in 1995. John Gangemi observed six female Harlequins in June 1995 on the Wigwam River, just north of the U. S. Canadian border in Alberta, indicating for the first time that this stream has a breeding population. Though breeding was observed in 1990 on Big Creek (Koocanusa) and Trout Creek (Superior), no birds were seen during 1995 pair surveys. Likewise ducks were seen in 1988 on Quartz Creek but not during this year's survey. A minimum of 151 pairs of ducks nest in Montana representing an estimated 198 total pairs; there are currently 33 Harlequin Duck Eos and 32 streams, surveyed 0-5 times each, where Harlequin Ducks have been observed or reported but on which the breeding status is unknown. Reproductive success, on streams surveyed both for pairs and broods in 1995, averaged 0. 23 broods per female; average brood size at or near fledging (Class III) was 3. 82. In Montana during 1974-1975 and 1989-1995, annual numbers of ducklings fledged per adult female averaged 1. 39 and ranged from 0. 13 to 3. 15 (n=305 adult females). Brood size (IIb to fledging) averaged 3. 59 and ranged from 2. 00-5. 86 (n=118 broods). The proportion of females successfully raising a brood in a single year varies widely between years. In Montana, stream surveys between 1974 and 1995 found 305 females raising 118 broods, for an average of 38. 7% (range 7-55%). We continued banding Harlequin Ducks in the Flathead and Clark Fork drainages. During 1995 in Montana, 10 adult males, 12 adult females, and 35 juveniles were captured and banded on 7 streams, bringing the total number banded since 1991 to 249 (39 males, 53, females and 157 juveniles). Adult males returned to their breeding streams from the previous year on 53% (n=51) of occasions, while females returned at a rate of 57% (n=81). A minimum of 24 birds banded in Montana have been sighted in Oregon (2), Washington (1), and southern British Columbia (21), including Vancouver Island and Hornby Island. Sexes and ages at banding show the following numbers and percentages observed: adult females (6, 11%), adult males (2, 5%), juvenile females (9,7%), and juvenile males (7, 5%). In Montana and Idaho, several relatively long-distance movements have been documented both within and between years. Two males and several breeding females were observed using different nearby drainages during different years, indicating that movements within a drainage of up to 30 km may regularly, but rarely occur. Of 100 ducklings marked in 1992-1993 in Montana, 14 females are known to have survived at least 2 years; of these, 5 were reported only from their natal stream, 1 only from the coast, and 8 from both the coast and the natal breeding stream. Seven males marked as juveniles were seen only on the coast; none have been reported from their natal stream.