Adult East Freisan crossbred (n = 220) and Chios ewes (n = 105) were divided into four groups and inseminated with chilled semen, which had been stored for 7, 13, 20 or 26 h at 5 degrees C. Unilateral intrauterine insemination (50 x 10(6) spermatozoa in 0.25 ml) was performed with the aid of a laparoscope. Inseminations were carried out 48 - 52 h after pessary removal (30 mg FGA) without detecting estrus. The lambing rates after intrauterine insemination with chilled semen were found to be similar in East Fresian crossbred (40%) and Chios ewes (30%). Intrauterine insemination with chilled semen stored up to 26 h resulted in similar lambing rates; whereas, fertility of Chios ewes tended to decline with increased holding time of chilled semen. From this study, it is concluded that decreasing the storage time of chilled semen at 5 degrees C improves pregnancy in Chios ewes and that East Fresian crossbred ewe's conception rates to intrauterine insemination with chilled semen was relatively higher than Chios ewes.