A protocol for conducting a 28 day sediment bioassay with the marine polychaete, Nereis (Neanthes) arenaceodentata is described. Primary application is the regulatory evaluation of dredged material. Test endpoints are survival and estimated individual growth rate. Bioassays are initiated by adding juvenile worms to 1L glass beakers (5 worms/beaker) containing aerated seawater (30 ‰) and 2–3 cm of sediment. Temperature is 20°C and photoperiod 12h. Worms are fed twice weekly, seawater renewed weekly and water quality monitored throughout. After 28 days, the number of survivors per beaker is recorded. Worms in each replicate are dried as a pool. Estimated individual dry weight is calculated by dividing number of survivors into the pooled dry weight biomass. Growth rate (mg dry weight day-1) is calculated by subtracting initial from final dry weights and dividing by the exposure period (28 d). Performance criteria for positive and negative controls are discussed as well as guidance for interpreting bioassay results. Although designed for the regulatory evaluation of dredged material, this chronic sublethal bioassay can be applied to other assessments of sediment quality.