Literature was reviewed to summarize fisher (Martes pennanti) population dynamics parameters. These parameters were included in a simple population model to estimate the annual finite rate of population change. Models combining lowest, unweighted mean, and weighted mean values of each parameter all indicated decreasing finite rates of population change, suggesting that most populations that have been studied rely on immigrationto remain viable. From 1992 to 1995 we studied the population dynamics of a lightly harvested fisher population in north-central Massachusetts. We captured nad radio-collared 92 (38 M, 55 F) fishers to estimate survival, reproduction and dispersal rates. Fishers dispersed 10-107 km (x̄ = 32 km) from area of capture. Dispersing fishers had a lower monthly survival rate than similar aged animals remaining in the study area and fishers that had completed dispersal. Territories of resident radio-marked fishers were mapped (approximately 55% of all territories), those of unmarked fishers were identified and the total number indicated an overall density of about 19 and 23 resident fishers/100 km2 for 1994 and 1995 respectively. Results from automatic camera, mark-recapture surveys also suggested a slight increase in the population from 1994 (16± 4 fishers/100 km2) to 1995 (25 ± 6 fishers/100 km2). Fisher track counts and numbers of fisher photographs also increased over the 2-year period. Survival, reproduction, and juvenile dispersal rates were incorporated into a simple population model and indicated a stable population (lambda = 1.0) However, an observed change in density (+ 21 %) over the period of study, confirmed observations that some immigration occurred. High adult female survival and reproduction combined with high dispersal rates suggest that this population is a "source" population for other areas with lower fisher densities or higher mortality rates. We implanted PIT tags in young kits (6-8 weeks old), juvenile (4-12 months old) and adult fishers (> 1 year old). When recaptured all PIT-tagged fishers had retained the PIT tag. However, 2 of 7 kits and 8 of 35 adults recaptured had lost both eartags, and 13 of 92 adult fishers shed their radio collar.