The present study has been made to study the effects of microcystin on the physiology of cockroach. Toxic effects of microcystin have been reported in rat, fish etc. this toxin effects the liver thus the metabolism of the organism is much affected. In cockroach, intracoelomic treatment of Microcystis extract showed some fluctuations in concentration of protein fractions especially in fractions 3, 4, 5 and 6. A common decrease in protein concentration is observed in 4, 5 and 6 but fraction 3 showed an increase in concentration. Fractions 7 and 8 failed to separate both in male and female cockroach. Reduced protein concentration for fraction 4 and 6 observed in male cockroach. The concentration of protein in the haemolymph generally decreases due to the microcystin treatment. Similar observation was recorded for the insects in spectrophotometric analysis of protein concentration.