This study was carried out to estimate combining abilities and heterosis in Single Comb White Leghorns. The data were obtained over a 500 days period from Apr., 1983 to Sep., 1984 at the Livestock Experiment Station. A total of 1,260 birds were reared, and these birds were composed of 630 pure strains,378 two-way crosses and 252 four-way crosses. Average amount of heterosis expressed as a ratio was 3.81% for viability, 1.73% for sexual maturity, 2.76% for hen-day egg production, 5.24% for hen-housed egg production, 6.11% for egg weight,-9.41% for feed requirement and 6.30% for body weight at 500 days of age. Special combining ability and reciprocal effects were statistically significant for all of the traits examined in this study. Although the general combining ability was not significant for any of the traits, strain V appears to be superior to other strains in general combining ability.