A nationwide screening program searching for microbial control agents of mosquitos was initiated in Malaysia in 1986. A total of 725 samples were collected and 2,394 bacterial colonies were isolated and screened for larvicidal activity. From such screening, 20 Bacillus thuringiensis, 6 B. sphaericus, 1 Clostridium bifermentans and 2 Pseudomonas pseudomallei larvicidal isolates were obtained. Of these, a new B. thuringiensis named as subspecies malaysianensis was found, while the C. bifermentans was also a new anaerobe individualized as serovar malaysia. It was concluded that this screening program was highly successful.