During the three years, 1964 to 1966, twelve species of introduced pasture crops have been tested for adaptation and production. Results obtained from the above test were used in analysing the seasonal productivity and summer depression of pasture crops in this report. Analytical results obtained are summarized as follows; 1. During the growing season, 66.2 percent of air-dry matter production of pasture crops was obtained before the beginning of July and after that date the production was less productive. 2. Of the species tested, bromegrass, fescue and birdsfoot trefoil showed the lowest seasonal variations in the production, and hybrid ryegrass, perennial ryegrass and timothy were the highest. 3. As the results, much more drought tolerant and more productive species during the summer were reed canarygrass, orchardgrass, and bromegrass, but ryegrasses, timothy and red clover were much less. 4. It was observed that the districts expected to have the highest summer depression, would be in the following order; Cheju, Chonju, Taegu, Kwangju, Mokpo and Yosu, the lowest; Ullung-Do and other districts belong to the medium. It was also estimated that the northern districts would be more adaptable for pasture production in considering the efficiency of production periods than the southern districts. 5. The results indicated the use of timothy for pasture improvement should be limited in those areas except high altitudes, and also the amounts of artificial mixtures of ryegrasses and red clover in permanent pasture should he reduced owing to their summer depression.