Random amplified polymorphic DNA analysis (RAPD) was conducted on isoproturon susceptible and resistant Phalaris minor populations from different wheat growing states in India for assessment of population diversity. Nine isoproturon susceptible populations from different wheat growing locations in India and 10 resistant populations from different locations in Punjab and Haryana states were analysed. Eleven random primers were used for amplification of DNA. Dissimilarity values amongst biotypes ranged from 0.049 to 0.95 indicating high level of heterogeneity among these populations. Cluster tree analysis grouped the biotypes into three major groups. The resistant biotypes were observed in all the three groups indicating the evolution of resistance to isoproturon in the three groups independently. Some of the populations showed resemblance with each other by amplification of common fragments indicating their common origin and spread to other areas possibly by cultivation practices and crop seed.