Cryoglobulinemia has been reported sometimes to cause false elevation in platelet and/or leukocyte counts in automated blood cell counters due to temperature-dependent protein precipitates that are falsely interpreted as blood cells at room temperature. Upon heating to 37°C, these blood counts decrease to normal levels as cryoproteins dissolve. Therefore, cryoglobulins could theoretically lead to erroneous diagnosis of spontaneous platelet aggregation in platelet counting and tur-bidometric methods as platelet count and turbidity of the platelet-rich plasma decrease at 37°C, respectively. Here, the event of pseudospontaneous platelet aggregation is confirmed in two patients with mixed cryoglobulinemia, both had spuriously elevated blood cell counts.