Four combinations of fish scrap, crab scrap and seaweeds were mixed with and enveloped in peat to examine the feasibility of preparing high quality composts from these materials. Neither lime, nor fertilizers were added. Each compost heap was built manually in the shape of a trapezoid with a base of 2m × 3m, and included two horizontal, perforated ventilation pipes. The air drawn naturally through the pipes, the fibrous and readily biodegradable nature of the peat, and the size and shape of the heap, allowed thermophilic (45° to 65°C) aerobic microbial activity to be attained within days. The aerobic activity was sustained so that neither H2S nor other malodours were emanated. No liquid was exuded. Nearly all of the NH3 produced during the composting was adsorbed as NH4+ by the moist, acidic peat. The water and heat retention properties of the peat minimized the need for watering or turning of the composts. The single turning of the heaps at the end of six or seven weeks did not cause reheating. The composts produced were free of phytoinhibitory substances, 5.9 to 6.5 in pH, earthy in odour, dark brown, granular, and contained 2.7 to 3.2% total N, 0.6 to 1.1% NH4-N, 0.2 to 0.5% NO3-N, 1.6 to 2.3% total P, 1.2 to 1.8% HCl-soluble-P, 0.35 to 0.70% total K, and 72 to 80% organic matter. The composts thus met or exceeded all criteria set for high quality.