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Normal platelets display a log normal size distribution pattern when analysed by an automated cell counter. Considerable changes in the platelet size distribution occurs during collection, processing and storage. This is easily monitored by the variation seen in the cellular indices or size distribution patterns. Platelet activation leads to a shift to the right whereas discoid/spheric conversion and microvesiculation/fragmentation are associated to shift to the left. Therefore changes in cellular indices are of value in assessing the dynamic shape changes and aggregation/disaggregation that platelet undergo during storage. We describe here an objective method for measuring platelet functional integrity based on cell counting. Our procedure is simple and based on the measurement of difference (d) of MPV before and after the addition of platelet samples to EDTA (4 ml dry dipotassium EDTA tube), incubating at 22 degrees C for a period of 1 h (for optimisation of shape changes and disaggregation) before counting. Since the platelet functional activity/aggregation states are pH-dependent we have investigated the effect of buffering condition on the functional integrity measured by dMPV. Both the standard and buffered EDTA exposure procedures appear to be suited for monitoring platelet functional integrity/aggregation and activation states but the standard EDTA protocol eliminates the need for pH determination hence is our preferred diagnostic tool, for platelet functional integrity and aggregation states.