We report the results of detecting M. lepraespecific antigen--phenolic glycolipid I (PGL--I) with modified M-Dot-ELISA in sera from 75 cases of household contacts (HC)of leprosy patients, which were all seropositive by Gelatin Particle Agglutination Test (MLPA)and ELISA. The results indicate that: (1 ) 16/75 (21. 3 % ) are antigen positive. The rates of positivity in HC of MB patients are much higher than those in HC of PB patients,the difference (P