The hybrid vigor that may be derived by crossing Minnesota inbred lines and line bred Sung Hwan lines has been Studied and Investigated since 1959 for the purpose of recommending Hybrid F₁ to the field flock owners. This is an intermediate report and complete one will be expected to come later The foundation stocks were from Minnesota inbred three (3) breeds White Leghorn (MWL), New Hampshire(MNH), White Plymouth Rock(MWR) and Livestock Experiment Station line bred three(3) breeds-White Leghorn(SWL), New Hampshire(SNH), Barred Plymouth Rock(SBR). The Minnesota breeds had been inbred during 1940 to 1950 and Sung Whan Livestock Experiment Station breeds have been line bred since 1952. Careful diallal crossing mating method was practiced between those six(6) during this experiment and the number of mating flocks covered in this experiment totaled as many as 36 flocks. 1. Hatchability. Among F₁ flocks, the SWL×MWR flock ranked highest of 94.47 and SBR×SNH flock ranked lowest of 46.3%, and SWL×MWR MWL×MNH and SWL×MNH flocks accompanied by appeciale significance and this fact was construe as an apparance of hybrid vigor. Though no significant differences were revealed by the statistical analysis, twelve(12) F₁ flocks showed increased heterosis compared with their parents. Three(3) F₁ flocks were in the same level in hatchability as either of the superior parental breeds and other nine(9) flocks maintained somewhat intermediate level between two parental breeds. In the mean time, rest of three (3) F₁ flocks were apparebtly inferior compared to their parents. The hatchability in terms of per centage may be expressed as follows: More than 91%……6 flocks 81-90%……10 flocks 71-80%……11 flocks 61-70%……7 flocks less than 60%……2 flocks 2. Body weight at eight (8) weeks age: Hatched F₁ progenies were healthy and active and the plumage was shining. Sung Hwan lines weighed more at eight weeks age than the Minnesota lines in general but cross breed F₁ progenies of those two lines were intermediate between their parents. Among their MNH recorded 338 gr of lowest and SNH marked 633.5 gr of highest. Among the F₁ flocks, in comparison with their parents. MNH×SWL and SBR×MNH flocks appeared increased heterosis and there were five (5) F₁ flocks no significant in terms of statistical analysis but weighing heavir than both their parental breeds and four (4) flocks were nearer to a heavier weighing parent. Further there were 11 F₁ flocks weighing somewhat between their parental breeds and three (3) F₁ flocks weighed less than their parental breeds. Among the reciprocal crossing of SWL(♂) with MWL(♀), MNH(♀), SNH(♀), MWR (♀), SBR(♀), and of MNH(♂), with MWR(♀), SBR(♀), and of SNH(♂), with MWR(♀), and SBR(♀) showed considerable differences in their respective body weights. 3. Chick mortality at eight (8)weeks age: Chick mortality at eight weeks age of MNH F₁ flock ranked in the highest of 40.91% and SBR followed next, and other flocks showed no significant differences. However it was noteworthy that there were no mortality at all among the F₁ flocks that crossed SWL (♂), with MWL(♀), MNH(♀), MWR(♀), and SWL(♀) with MNH(♂). However five (5) flocks appeared heterosis in spite of no significant differences being noted in terms of statistical analysis, and except two F₁ flocks that showed recessive than their parental brads. rest of other F₁ flocks were between their parents records. In the mean time it was understood that there were less mortality among the F₁ flocks that were crossed SBR(♂), with Minnesota linen (♀). In general no significant differences were noted among F₁ flocks.