A comparative Genetic-Epidemiological analysis was carried out in HarGl'i Region of Ethiopiarn(Region-I3) on the spectl1lm, ji-equency, and distribution of some selected human traits whichrnhave been described by several previous scientific investigations as being geneticallyrndetermined: (I) Genetic diseases which arefolllld under various disease classification categoriesrnof the Ethiopian Minisfly of Health's "List of Causes for Tabulation of Morbidity and Mortality"rnand (2) the ABO blood groups. From all available medical data of IO-years (I984-I994 E.C.), arntotal sample of more thanI2,OOO cases of the various selected disease conditions were collectedrnji-om hospital inpatient belonging to different Population Categories (PCs) characterized byrndifferent 'Local Ethno-Geographic' backgrounds; and 279 blood samples were taken ji-Olllrninformed volunteers of the normal population with different ethnic origins-Oromo, Amhara, alldrnHarGlÂ·i. The genetic disease samples collected ji'Oln hospital records of inpatient populationsrnwere grouped into four basic PCs that closely follow or approximate their historical settlementrnpatterns as well as current administrative boundaries of HarGl'i Region, which are bothrnpresumed to be based upon and reflect the ethnic identities or composition of their respectiverninhabitants; the blood samples were grouped into three groups based 011 the ethnic origin of thernvolunteers. (1) The statistical analysis results with regard to the RFD of disease traits were foundrnto be age and sex specific among the compared PC pairs. PC-I was found to be the mostrndistinctive population categOlY of all in its RFD of those disease traits classified under Dxgroup-rn2 (Neoplasms), Dxgroup-3 (Deficiency Diseases- Diabetes Mellitus and Diabetes Insipidus), andrnDxgroup-6 (Diseases of the Nervous System and Sense Organs- Epilepsy, Cataract, andrnGlaucoma). PC-I showed no significant variation ji-om any of the other PCs ill its RFD ofrnDxgroup-I (Malaria), Dxgroup-9 (Diseases of the Digestive System), Dxgroup-IO (Diseases ofrnthe Genito-UrillGlY System), and Dxgroup-II (Diseases Associated with Pregnancy, Child Birth,rnand the Puelperium). (ll) The statistical tests concerning the ABO blood group samples obtainedrnji'Oln the three major ethnic groups in HarGl'i Regioll showed that (1) Phenotypic heterogeneityrntest: the total chi-square values for homogeneity were nOll-significant both among the (i) Oromo,rnAmhara, and HarGl'i entries, and (ii) Oromo and Amhara entries with Chi-square=5.932, df=6,rnp>O.05 and Chi-square=4.332, df= 3, p>O.05, respectively, indicating phenotypic homogeneity.rn(Similar tests on the other possible data combinations could not be pelformed due to insufficientrnrndata.) (2) Genetic-equilibriulll test: (i) the Chi-square values for genetic equilibrium were nonsignificantrnfor both the Drama and Amhara entries indicating random intra-ethnic mating to thernextent of reaching genetic equilibrium, (Similar tests on the Harm'i enl1y could not be pe/formedrndue to insufficient data.) (ii) the total Chi-square values for genetic equilibriulll were IlOnsignificantrnfor the combined entries of the Drama, Amhara, and Harm'i as well as the combinedrnentries of the Drama and Amhara indicating either that (a) there is random inter-ethnic matingrnbetween the populations ji'om which the samples were taken, or (b) the samples were taken ji'01l!rndifferent ethnic populations each of which are randomly mating within themselves and are all atrngenetiC equilibrium as well as possessing similar proportions of the alleles at the ABO locus, (iii)rnthe total Chi-square vailles for genetic equilibrium were significant for the combined entries ofrnthe Drama and Harm'i as well as the combined entries of the Amhara and Harm'i indicating thatrnthe Harm'i do not engage in random inter-ethnic reproductive mixing with neither the Amhararnnor the Drama, although they are genetically closer to the later than the former ethnic group,