This study was carried out to determine the dosage of PMS for increasing the rate of multiple births in Korean native cow. Animals were injected subcutaneously with 50G, 750, 1,000IU PMS, respectively on day 17 of the oestrus cycle followed intravenously by 1000IU HCG at the onset of the next oestrus (Only 1-2 Graffian follicles). The results obtained were as follows; 1. Most. of the cows treated witty 1000IU PMS exhibited normal oestrus behaviour(87.5%) and those treated with 500ICT revealed the poorest oestrus rate (56.6%) among the treatments. 2. Duration from the injection time with PMS to the onset of estrus was 4.8 days and was no significant difference among the treatments of various dosages of PMS. 3. The mean number of matured follicles per cow treated with 1000IU PMS was 1.3.