Several weeds of rice in Australia have developed resistance to the main herbicide available for their control. Allelopathy is one phenomenon that could be incorporated into an integrated weed-management system as a supplement or alternative to synthetic herbicides. Several rice cultivars were screened both in the laboratory and the field for allelopathic potential against a major rice weed, Damasonium minus. Results from the laboratory bioassay showed that there were significant differences among cultivars in their ability to inhibit D. minus root growth. D. minus root lengths ranged from 2.0% (cv. Hungarian # 1) to 32.6% (cv. Rexmont) that of the control. In the field study, significant differences existed in the D. minus dry matter grown in association with different cultivars, ranging from 4.6% (cv. Tono Brea) to 72.2% (cv. Rexmont) that of the control. Comparison between laboratory and. eld results indicated a strong relationship between performance in the field and in the laboratory (r(2) = 0.713). Those cultivars ranked as allelopathic in the bioassay tended to have associated lower D. minus dry weight in the field. Eight of the top 10 allelopathic cultivars in the bioassay were among the top 10 suppressive cultivars in the field trial. This important. finding indicates that at least some of the variation in field performance of cultivars may be predicted by their performance in bioassays.