Gastric cancer is one of the most frequent malignancies and its treatment is far from satisfactory. The challenge to oncologists is the characterization of novel chemical entities with greater effectiveness. Prodigiosin is a red pigment produced by various bacteria including Serratia marcescens. Here we characterize the apoptotic action of prodigiosin in human gastric carcinoma cell line (HGT-1). Cells were assayed by the MTT assay, fragmentation pattern of DNA, Hoechst 33342 staining and study of actin microfilament architecture. Treatment of these cells with prodigiosin showed a constant decrease in viability by apoptosis. Morphological analysis of prodigiosin-treated cells demonstrated that prodigiosin induces cell shrinkage, chromatin condensation, reorganization of actin microfilament architecture, and detachment of cells from the cell culture substrate. Altogether these results suggest that prodigiosin induces apoptosis in HGT-1 human gastric cancer cells and raises the possibility of its use as a new chemotherapeutic drug.