The toxicity of cadmium on Caenorhabditis elegans was investigated to identify sensitive biomarkers for environmental monitoring and risk assessment. Stress-related gene expression were estimated as toxic endpoints Cadmium exposure led to an increase in the expression of most of the genes tested. The degree of increase was more significant in heat shock protein-16.1, metallothionein-2, cytochrome p450 family protein 35A2, glutathione S-transferase-4, superoxide dismutase-1, catalase-2, C. elegans p53-like protein-1, and apoptosis enhancer-1 than in other genes. The overall results indicate that the stress-related gene expressions of C. elegans have considerable potential as sensitive biomarkers for cadmium toxicity monitoring and risk assessment.