Weed density and yield of rice in western IGP were examined in transplanted rice crop under rice-wheat, rice-pea-rice and rice-sugarcane=ratoon-wheat/fallow cropping systems. Echif/ochloa crusgalli was dominant after rice-wheat and rice-pea-rice sequence, but it was completely suppressed after the sugarcane sequence. Among sedges, Fimbristylis milliacea was dominant after rice-wheat and Cyperus difJormis after rice-pea-rice. [n the sugarcane system. Cyperlls rotllf/dlls became the main weed. The yield loss from weeds in unweeded plots was highest in the rice-wheat system. followed by rice-pea-rice, and was least in the sugarcane system. Under fanners' weed management practices, there were yield losses due to weeds ranging from 13.1 to 22.4'Yo. The total cost of weed management in transplanted rice was higher in rice-wheat system than in rice-pea-rice or rice-sugarcane system.