A life table response experiment lasting 120 d was used to investigate the effects of the synthetic polycyclic musk HHCB (1,3,4,6,7,8-hexahydro-4,6,6,7,8-hexamethylcyclopenta-γ-2-benzopyrane; 0, 1.5, 26, 123, and 168 mg/kg dry wt sediment) on the life history of the infaunal polychaete Capitella species I. The HHCB exposure showed no detectable effects on adult survival, age at first reproduction, length of the reproductive period, number of broods, individual worm body volumes, or body size-specific egestion rates. In contrast, HHCB significantly affected juvenile survival (≥123 mg/kg), maturation time (168 mg/kg), total number of eggs produced (≥26 mg/kg), and brood size (≥123 mg/kg) and marginally increased time between breeding attempts (≥26 mg/kg). A declining trend was observed for population growth rate with increasing HHCB concentrations, but differences between the control and exposed groups were not significant. Thus, despite detectable effects of HHCB on individual life-history traits, the results suggest that environmentally realistic concentrations of HHCB are not likely to reduce the growth rate of Capitella sp. I populations.