The study is aimed to investigate the effect of lamivudine on growth and metabolism of three intestinal characteristic bacteria (namely, Bifidobacterium adolescentis, Escherichia coli and Shigella dysenteriae). The growth condition of the three bacteria was quantitatively evaluated by microcalorimetry with four characteristic parameters of the thermal power-time curves, including the growth rate constant (k), thermal power (p), time to peak (t) and calorific value (Q). The results showed that the IC50 value of lamivudine on B. adolescentis was 200 microg x mL(-1), and the IC50 values of lamivudine on S. dysenteriae and E. coli were higher than 3 000 microg x mL(-1) and 6 000 microg x mL(1), respectively. Therefore, lamivudine made different inhibitory effects on the three bacteria, in which the B. adolescentis was most susceptible to lamivudine. This work showed that taking lamivudine chronically is likely to affect the balance of good flora in the intestinal tract, and might increase endotoxin release, leading to inflammation and disease progression in hepatopathy.