This paper describes the distribution of the first milk somatic cell counts (SCC) measured between 5 and 14 days of lactation, during a one year period (1999) for 12,994 dairy heifers on 3,221 herds in Flanders (Belgium). Somatic cell counts ≤ 150 x 103 cells/ml were allocated to class 1. Somatic cell counts between 151 x 103 and 3000 x 103 cells/ml, between 301 x 103 and 1,000 x 103 cells/ml and >1,000 x 103 cells/ml were allocated to classes 2,3 and 4, respectively. The prevalence per class was 65.4, 15.6, 12.9 and 6.1% for classes 1, 2, 3 and 4, respectively. The within-herd prevalence for class 1 varied from 27.3 to 100%, with a median of 66.7%. For classes 2, 3 and 4, the median within-herd prevalence was 15.4 (range: 0.0 – 50.0%), 10.0 (0.0-54.5%), and 0.0% (0.0-30.0%), respectively.