The lite cycle of Moniliformis dubius Meyer, 1933 was investigated by using rats (Rattus norvegicus) as the definitive host and American cockroach (Periplaneta americana) as an intermediate host. At room temperature (22-26 degrees C), the shelled acanthor hatched in mid-gut of P. americana 3 days postinfection. released to be the acanthor and then penetrated the gut wall into the hemocoel 5 days postinfection. It further developed into acanthella with proboscis primordium 16 days postinfection. The cystacanth stage recovered 45-52 days postinfection. Rats were fed with the cystacanth, their intestine and feces were examined daily. Shelled acanthor was found in feces on the 31st day of the infection. From the above results, the life cycle of M. dubius was completed within 76-83 days. Observation of the mature adult by scanning electron microscope, both sexes were similar in morphology.