Twenty-seven F4 lines and their parents (Rikuto Norin 22 and Sakha 101) were evaluated to blast disease (caused by Pyricularia grisea) and allelopathy under greenhouse and field conditions at Rice Research and Training Center, Sakha, during 2001 growing season. The results indicated that, six of 27 F4 lines had more than 85% allelopathic potential to the barnyardgrass against Echinochloa Crus-galli comparing with the check variety Giza176 (zero allelopathic potential). However, four lines from the six had more than 94.4% weed control. On the other hand, twenty-four, twenty and fourteen entries were resistant to blast races ie. II (avirulent), IA-79 (moderately virulent) and IA-107 (virulent), respectively. The rest of lines were moderately resistant or susceptible to blast under greenhouse conditions. The same trend was obtained under field conditions, seventeen entries were resistant, two moderately and eight susceptible to leaf blast disease. Highly significant positive correlation were found between weed control percentage and each of grain yield and harvest index. Insignificant negative correlation were obtained between weed control and each of days to heading and blast disease in green house and field conditions. In general, no relationship was found between allelopathic effect and blast resistance. Accordingly, selection to blast resistance or allelopathic potential should be done separately.