Sediments, water, and oysters from the receiving waters of the Hahaione Valley, a suburban development in south-easter Oahu, Hawaii, were analyzed for organochlorine pesticidal compounds. The insecticides dieldrin, alpha- and gamma- chlordane, and p,p'-DDT were found in the study site environment. Levels were in the low parts per billion range for oysters and sediments and in the low parts per trillion range for water. During the past several years dieldrin residues in the marina study site have increased, even though the only activity known to influence pesticide levels in the valley is the chronic treatment for subterranean and dry wood termites. If present trends continue, dieldrin may pose a threat to biota of the aquatic environment. Findings have shown that residue levels of dieldrin and p,p'-DDT in the sediments are within the LD50 (median lethal dose) range for estuarine fish and thus may have a deleterious effect on bottom-feeding organisms. According to present standards of the Food and Agriculture Organization/World Health Organization, pesticide residue levels within the study site do not appear to constitute a health hazard to humans.