The present investigation was conducted to realize the feasibility of heterosis breeding method using three lines system in rice (CMS. maintainer and restorer lines). The experiments were carried out during 2002. 2003 and 2004 growing seasons at RRTC Farm. Sakha. Kafr El-Sheikh, Egypt. Twelve hybrids obtained from crossing four diverse CMS lines as females with three Egyptian restorer lines were evaluated along with the parents for genotypic variation. The mean squares of the genotypes showed significant values for all studied grainn quality characters at the two years and their combined data. indicating the presence of large variations among them. The interactions of genotypes and parents with years were insignificant for all grain quality characters with the exception of total milled rice % (TMR %) and Head rice %(HR %) which should highly significance mean squares. The interaction of crosses _with the years was found to be insignificant for all characters except HR%. in the mean time. the interaction of parents vs. crosses with the years was significant for TMR%. HR%. grain shape and Chalkiness of endosperm (CLK) and insignificant for BRO/o, Brown rice length (BRL). gelatinization temperature(GT) and amylose content % characters. The analysis of variances for combining ability revealed significant differences among CMS lines for BR%. BRL%. grain shape. CLK. GT and amylose content %. Therefore. the testers exhibited significant differences for BRL. grain shape and GT. The line x tester (SCA) variance exhibited significant differences at the two years and their combined data for HR% and amylose content % and varied for the rest of grain quality studied characters. The result .alsoindecated that the parents . IR58025A. IREBBBSA. Giza 178 R and Giza 182 R were found to have favorable genes for one or more characters along with grain quality. Out of 12 hybrids one hybrid for BR%. two for HR%. one for grain shape and three for low amylose content exhibited significant desirable SCA effects in the two years and their combined data. The superior hybrids for most grain quality characters were SK 2003 H (G. 46NGiza 178 R), SK2010 H (G. 46NGiza 182 R) and SK 2011 H (large stigma NGiza 182 R). The estimates of genetic parameters revealed that additive variance values and relative importance of GCA% were higher than these dominant variance and relative important of SCA% for all grain quality studied characters except in case of BR%.