The spotted spiny lobster, Panulirus guttatus, is a reclusive, reef-dwelling species and appears to be restricted to coral reef habitat for its entire benthic existence. Little is known about its population dynamics, and much of the data that are available is derived primarily from trap-caught individuals and may therefore be biased. We avoided this problem by diving at night on patch reefs in the Florida Keys (U.S.A.) to collect lobsters when they are most accessible and used mark-recapture methods to estimate their growth and size at maturity. Molt increment for lobsters greater than 50 mm CL was estimated to be 1.5 mm for females and 1.6 mm for males, while molt interval was 50.6 weeks for females and 50.0 weeks for males. Growth rate was calculated to be 0.02–0.37 mm CL/week depending on size and sex. On average, males grew faster than females, but the rate of growth decreased with increased size for both sexes. Female size at maturity was estimated at 32 mm CL, based on both the minimum size of egg-bearing females and the size at which 50% of the females produced eggs. We estimated size at maturity for males to be 36–37 mm CL, using the onset of allometric growth of the second walking leg as an indicator of male maturity. Panulirus guttatus is a diminutive species, and its size at maturity is small compared to other species of spiny lobster, although its growth rate is comparable to other species. These unusual life history characteristics may reflect selection for traits advantageous to life in small, architecturally complex habitat patches.