In recent years, microarray technology has enabled the investigation of possible mechanisms the expression of genes related to toxic compounds. We used a C. elegans whole genome microarray to observe and evaluate the chronic toxicity of the free-living nematode Caenorhabditis elegans (C. elegans) after exposure to octachlorostyrene, (OCS), a by-product in the manufacture of many chlorinated hydrocarbons. In this study, we examined sublethal toxicity, egg hatching, and movement of octachlorostyrene over three generations using a nematode growth medium (NGM) agar plate. In the third generation, OCS affected the fecundity rate of C. elegans. Specifically, the number of worm and eggs decreased significantly to about 50% of control (p < 0.05). In microarray experiments, total RNA was isolated at 0, 2 and 3 generations following treatment of OCS, and hybridized to the microarray containing about 22,000 C. elegans genes. Dye swaps were performed. After data analysis, we identified a total of 1,294 genes that were differentially expressed through generations.