To examine the expression profile of oxidative stress responsive genes in Spodoptera litura, we constructed a cDNA library from S. litura injected with hydrogen peroxide (H2O2). Using a microarray chip composed of 2,964 cDNAs, we screened gene expression at 1, 3, 5, 7, and 9 h post H2O2 injection. Data were clustered into 15 groups of genes that behave similarly across each time course. Seventy-three genes were identified as being at least 2-fold up- or downregulated after treatment with H2O2 in S. litura. We constructed expressed sequence tags (ESTs) for genes that changed at least 2-fold after treatment with H2O2. The functional classification of these ESTs based on Gene Ontology showed that the ESTs are rich in genes involved in oxidoreductase activity (5.7%), defense (14.3%), cellular process (22.9%), and development (17.1%).