Summary: The IgG and IgM reactivity of sera from lepromatous (LL) and tuberculoid (TT) leprosy patients was analysed by enzyme immunoassays (EIAs) based on three different antigens of M. tuberculosis (H ^ Rv) i.e. sonicate supernatant (SS), purified protein derivative (PPD) and intact cells (1C). The predominant response of LL and TT sera with the three antigens was of IgG type. The IgG as well as IgM reactivity of LL sera was higher than that of TT and normal sera. The IgG and IgM reactivity of LL and TT sera was maximum with 1C, followed by that with PPD and SS antigens, in that order. This pattern was qualitatively and quantitatively different from that of tuberculosis sera reported previously (Agarwal & Moudgil, 1988)