Somatic cell count samples (SCCS) for use in calibration of milk somatic cell counting methods were prepared from raw bulk milk preserved with potassium dichromate. Somatic cells were separated by centrifugation, then appropriate cell dilutions were prepared in the dichromate-preserved skim milk. Somatic cell counts from SCCS stored at 4°C were stable over a 23-wk period. No bacterial contamination was detected in these samples. In a collaborative study among eight laboratories, SCCS were not affected by usual conditions by shipping. The SCCS can be used as reference standards for the direct microscopic somatic cell count and the Fossomatic and Coulter Counter somatic cell counting methods.