Determination of combining ability of the yield trait of some inbred maize lines by diallel method NguyÔn ThÕ Hïng1 Summary A diallel experiment involving nine inbred lines: T13, T14, T15, T16, T17, T18, T19, T20 and T21 selected by the National Maize Research Institute in autumn - winter crop season 2002 and in spring season 2003. The software Diallel was employed to evaluate the combining ability (CA) of the yield trait. Two lines, T16 and T18 had good general combining ability (GCA). Based on the specific combining ability three outstanding combinations, viz. T14 x T16, T18 x T20 vµ T19 x T21 were identified. These combinations had short growth duration (112 -118 days in spring season), reasonable plant height (190 - 200 cm), good tolerance to pests and diseases and higher yield. These three combinations are recommended for further yield trial. Key words: Diallel cross, yield, general combining ability and specific combining ability.