To test functional hypotheses about home-range variation, it is necessary to compare the fitness of individuals whose home ranges are characterized by measurable differences in vital resources such as mates and food. In the present study, we compare measures of reproductive success of male lizards estimated from field observational data with results from DNA fingerprinting of the same individuals. Observational data included both male and female home-range overlap and proximity of actual sightings. Because home ranges can function for access to mates, and males with larger home ranges can overlap a greater number of females, we tested the hypothesis that males with larger home ranges have higher reproductive success. We also tested to see whether females were most likely to mate with males that overlapped their own home range. We found a positive correlation between male home-range area and the number of females overlapped by a male. Male reproductive success was not significantly correlated with home-range area but was positively associated with the number of females overlapped by a male home range, even after the effect of body size had been statistically removed. Despite this relationship, only about 40% of our observational estimates of reproductive success were confirmed by DNA fingerprinting in this population. Thus, many females had mates whose home ranges did not overlap their own, and proximity of a male to a particular female did not accurately predict paternity.