Pyrethrins I and II were extracted from five seasonal Compositae herbs collected from semi-arid and hilly areas of North India. The relative toxicity of natural pyrethrins were evaluated against Mesocyclops leuckarti sensu lato. Based on the LC50 values, the extract of the plants could be arranged as follows: Tagetes minuta > Pulicaria crispa > T. patuia > T. minuta > P. angustifolia.