The haemodynamics of CL during natural and induced luteolysis was studied in crossbred cattle using colour Doppler ultrasonography. In natural cycle, penetration of Doppler signals deep into the CL was observed during Day 15 – 17 coinciding with the initiation of luteolysis. When PG was administered in the early luteal phase (Day 4), there was an increase in blood flow intensity in the periphery of CL, but when PG was administered in the mid luteal phase (Day 10), the intensified Doppler signals penetrated deep into the luteal parenchyma within two hours. There were no significant differences in velocity parameters and RI values between the treatment groups. Thus it was concluded that the characteristic difference in the intensity and nature of vascular perfusion was the determining factor for the initiation of luteolytic process in cattle.