ABSTRACTThe mean packed cell volume (PCV) for canine blood samples received by post was significantly higher than that for fresh samples, at each haemoglobin value over the range 9 to 19 g/dl. As a consequence the mean corpuscular volume (MCV) and the mean corpuscular haemoglobin concentration (MCHC) also differed. Apart from one Hb value there was no significant difference in the mean red blood cell (rbc) count over the Hb range 6 to 14 g/dl. It is suggested that the normal values for the PCV and MCV should be 3 to5%and 5 to 7 f 1 higher respectively for postal samples as compared to fresh samples while the MCHC should be about 3 to 4 g/dl lower.