The need for larger sheep has compelled both the consumers and sellers in the middle and Southern parts of Nigeria to frequently opt for giant breeds of sheep from the Northern parts of the Country. Balami and Uda are the two largest Nigerian breeds of sheep and therefore have the potentials of improving, through crossbreeding, the body weight of small body-sized West African Dwarf (WAD) sheep. The objectives of this study were to determine: (i) the morphometric characteristics of traditionally managed WAD, Balami and Uda sheep; (ii) reproductive and growth performance of pure and crossbred sheep; (iii) heterosis, repeatability and heritability of economic traits; and (iv) best morphometric descriptors of body weight in pure and crossbred WAD, Balami and Uda sheep in Nigeria. rnThree experiments were conducted. Experiment 1compared the morphometric traits of 1017 traditionally managed sheep within North and Central Nigeria. Experiment 2 evaluated thegrowth and reproductive performance of pure and crossbred Uda, Balami and WAD Sheep using an unbalanced design, while Experiment 3assessed the heritability and repeatability of growth traits and best morphometric descriptors of pure and crossbred sheep. Data collected were subjected to Analysis of Variance using a model of Factorial Design (pË‚0.05). rnThe findings of the study were that:rni. traditionally managed Balami sheep was superior to Uda and WAD in all morphometric traits. Males were superior to females in all morphometric traits.rnii. WAD sheep had the highest conception (80%) and lambing rate for all the parities (80%);rniii. lambsâ€™ birth weights increased with damsâ€™ age and parity;rniv. crossbred lambs were superior over purebred WAD in all morphometric traits both at birth and at yearling stages;rnv. heterosis for body weight in Uda crossed with WAD was higher than in Balami crossed with WAD at birth (24.70% and 22.42% respectively) and at weaning (9.25% and -4.84% respectively); rnvi. WAD had higher repeatability for body weights (0.99) and total milk yield than other breeds; andrnvii. WAD sheep group had the most accurate classification (92.4%). The Dendogram plot showed WAD sheep was closer to Uda than Balami while Uda crossed with WAD sheep was closer in body weight to the purebred Uda sheep.rnThe study concluded that genetic resources of Nigerian breeds of sheep could be described using morphometric traits. Crossbred sheep were superior to the purebred WAD sheep in morphometric traits, lamb birth and weekly body weights. The study recommended that to improve weaning weight, Uda sheep should be crossed with WAD sheep. However,to improve yearling weight,Balami sheep should be crossed with WAD sheep.