Fourty-eight mongrel dogs were bled to half the level of their control aystolic blood pressures and infused with Hartmanns solution+low molecular weight dextran, whole blood, or with Hartmann's solution, low molecular weight dextran (1:1 or 1:3) in the amount equivalent to the blood loss. Bleeding time, coagulation time, platelet count and erythrocyte sedimentation rate were examined 6 hours and 24 hours after the completion of infusion. The results are as follows: 1) No changes in blood coagulability other than due to hemodilution were observed in dogs infused with Hartmann's solution, whole blood, or 1:1 Hartmann's solution+low molecular weight dextran. 2) Significant changes in blood coagulability were noted, however, in dogs infused with low molecular weight dextran alone or 1:3 Hartmann's solution+low molseular weight dextran. These changes seem to be related rather to decreased platelet function than to the decease in platelet number.