This study aimed to detect the incidence of subclinical mastitis (SCM) in the milk of dairy cows in Sohag city, Egypt. 100 quarter milk samples from all quarters of 25 dairy cows with apparently healthy udders were examined by strip cup test, California mastitis test (CMT), White side test (WST), chemical and bacteriological tests. From the obtained results, it was found that none of the strip cup test was positive, while CMT revealed 53% positive with various degrees, and the WST revealed 49% positive with various degrees. According the estimation of chloride % and lactose %, the Koestler number was revealed 33% mastitic, 25% suspected and calculated 42% normal samples. According the bacteriological examination, out of the 39 bacterial isolates from the examined milk samples, Staph. aureus, Strept. agalactiae and E. coli were estimated 64.10%, 28.21% and 7.69%, respectively.