Stepwise multiple regression analysis was carried out during 1998 and 1999 seasons using ten Egyptian cotton varieties i.e., Giza 83, Giza 45, Giza 84, Giza 70, Giza 75, Giza 76, Giza 77, Giza 79, Giza 85 and Giza 81 to study the effective variables that accounted for the variance of lint yield/plant.  The results indicated that number of open bolls/plant was the variable that exerted the greatest influence on lint yield/plant and contributed about 84.55%, 79.14% and 90.55% of the total lint yield variation in 1998, 1999 and combined analysis over the two seasons, respectively.  Lint percentage and boll weight contributed about 8.90%, 4.60% and 2.0%; and about 4.94%, 12.39% and 6.48% of the total lint yield/plant variation in 1998, 1999 and combined analysis over the two seasons, respectively.  This study indicated that number of open/boll was the major and the most consistent source that account for variation of total lint yield/plant, therefore, this trait must be considered in any breeding program for increasing yield of Egyptian cotton.  The data indicated slight discrepancy between p.c.v. % and g.c.v. % for the most studied traits, reflecting the high estimates of genotypic variances.  The genotypic and phenotypic correlation among pairs of traits over the two seasons, as well as the stepwise prediction equation and implications of the present results in breeding programs were discussed.