The aim of the study was to determine the causes of lactating cow culling that influence the length of cow utilization in dairy herds. Data regarding number of culling, parity at culling and reason(s) for culling were collected in a one year survey, carried out from 21st March 2006 to 20th March 2007 in 15 commercial Holstein dairy herds in Mashhad suburb capital of Khorasan Razavi province located in north east of Iran. Average culling rate in these farms was 24%. Out of a total of 650 culled cows, the proportions of culls for udder disorders; infertility or reproductive disorders; lameness; emergency culling reasons; displaced abomasum, other health disorders; low milk yield and sales for dairy purpose were 17.2, 22.1, 5.5, 6.7, 5.8, 38.7, 3.1 and 0.9%, respectively. Parity at culling for about 80% of culled cows was 4 or less and it’s average was 3.2. Cows culled for displaced abomasum and emergency culling reason were younger and their mean parity was about 2.6. In contrast cows culled for low milk yield and sale for dairy reason left herd at higher parity. Cows culled for other reason were more frequently at parities 3-4. Health disorder was the main reason of culling in these dairy herds. Voluntary culling was lower compared to other studies elsewhere in the world. Culling of highly percent of cows at low parity because of health disorders could be contributing to economic loss. However, some priority should be given to reduce culling at young age specially for health disorder that is the most important and so the most costly exit reason

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