This is the first portion of the reports on my series of research to be undertaken to provide the basic data relevant to the task of up-leveling the hitherto low rate of Korean farm cattle reproduction to ease the recent press of meat demand in Korea. The most consequential of the causes for retarding the reproduction rate was the delay of first alving; the prolongation of delivery interval came next as the cause, and quite a number of the sterile cows also deteriorated the over-all reproduction rate. The causes that delayed the first delivery of the first calved cows and prolonged the delivery intervals of the calved cows were: first, that the intervals between the birth and the first heating in the case of the first calved cows and the interval between the delivery and the repeated heating in the case of the calved cows were unduly prolonged, and second, that, in either case of the first calved cows and the calved cows, the first heating was not met with mating and even the second or third heating may have passed un-mated, or even when the first heating was mated, it may have resulted in no fertility, necessitating the repeated coatings. To find out the causes and process that produced so many sterile cows, the writer also conducted on extensive research over the three kinds of sample farm cattle each representing the high altitude mountainous zone, the low altitude flat land and the intermediate zone respectively, and obtained the below listed conclusions: 1. Measures must be taken to quicken the heating for the 36.6% of the first calved cows whose interval between the birth and the first heating was more than 24 months and the 47.9% of the calved cows whose interval between the delivery and the repeated heating was more than 3 months. This heating quickening project should be started in the low altitude flat land where are comparatively large number of the first calved cows and the calved cows whose heating takes longer interval, and then gradually be extended to the other two zones. 2. The 40% (the first calved cows) -34% (the calved cows) of cattle whose mating was met at the second or third heating must be mated at their first heating. This mating quickening project should be started at the low land zone where mating is practiced largely at the heating coming after 2 or more empty heatings, and then gradually be extended to the other two zones. 3. Measures must be taken to fertilize the 20%(the first calved cows) -18%(the calved cows) of cattle whose fertility was realized at the second or later mating. For the first calved cows, the project must be started at the high altitude mountainous zone where are majority of the first calved cows whose fertility was realized at the mating later than the first mating, with the gradual extension to the other two zones. For the calved toms, the project should be started at the low land farm zone where majority of the calved cows are fertilized at the mating later than the first mating, with the gradual extension to the other two zones. 4. The below listed, ordered in frequency, are the causes that retarded the mating at the first heating of the first calved cows: a) The mating delay coming from the poor growth, b) No reason identified for the mating delay, c) The heating was detected too late, d) The mating was purposedly delayed to utilize the cow for farming, e) There was no bull or an artificial insemination point nearly, f) Other causes unknown. In the case of the calved cows, the causes were almost the same as those listed above with the frequency order modified as c)-b)-a)-d)-e)-f). 5. The causes for no fertility in spite of mating for the first calved and calved cows are listed below in the order of frequency: a) Mating was too late, b) Un-identified reason for no fertility, c) Un-suitability of bull, d) The technical shortage of artificial insemination, e) The diseases of the cow`s reproductive organs, f) The causes unknown. 6. The rate of no fertility wa