The survey was conducted on February 1981 and 1982, throughout the rice growing area of Chile. Twenty five species were determined as weeds that might be causing losses in rice production. Nine species are reported for the first time present in the country. The species collected are indicated in Table 2. The most frequently found were: A. plantago, C. difformis, C. era grostis, C. palustrís, E. crus-galli, P. distichum and J. repens var. montevídensis. Less frequent, but mportant, were: E. ovata, S. mucronatis and C. brongniartti.