Grain filling rate in wheat (Triticum aestivum L . emend . Thell .) positively influences grain yield under a wide range of conditions . The effective utilization of this trait in breeding depends on an understanding of its genetic control . A study was, therefore, conducted to determine the genetic basis of grain filling rate in six crosses of wheat . Higher order genic interactions and/or linkage were important in the genetic regulation of grain filling rate (GFR) in the majority of crosses . Additive ([d]) and dominance ([h]) gene effects were important in the control of GFR in main ears (ME) and whole plant ears (WPE) . Additive and additive x additive epistatic effects were the most important in the genetic control of GFR in last ears (LE) . Location effects on genetic effects for GFR were significant (P < 0.05) in all ear types of some crosses except in ME. Genotype x environment interaction effects were important (P < 0 .001) in LE and WPE .It was concluded that the inheritance of GFR is complex and is dependent on ear type . Breeding procedures that facilitate the exploitation of non-additive and additive gene effects were recommended for the genetic improvement of grain filling rate of wheat .