Abstract: As the dairy industry continues to strive for increased genetic gains in milk production, cows will continue to be at increased risk of developing ketosis. Subclinical ketosis is defined as increased levels of circulating ketone bodies without the presence of clinical signs of ketosis. In this study, subclinical ketosis incidence in dairy cows in Fars province of Iran and its correlation with some reproductive performance values was investigated. A total of 167 cows in 14 Holstein crossbreed herds were monitored for subclinical ketosis in a period of calving to 70th day postpartum, weekly. Milk samples were collected and the level of milk ketone bodies was determined qualitatively by the use of nitroprusside milk test. The incidence rate of subclinical ketosis was 7.2% (percent of cows with at least one positive test) in early lactation (0-70th day) period and the peak prevalence of subclinical ketosis occurred during the fourth week of lactation and there was no significant difference between positive and negative groups in reproductive performance values.