ABSTRACT:The aim of this experiment was to find out the in-vitro effects of the extracts of certain plants, considered to have medicinal value, on the erythrocyte model. The plants, selected for the study, were Tulsi (Ocimum tenuiflorum), Neem (Azadirachta indica) and Amla (Phyllanthus emblica).Three different concentrations of leaf extracts were prepared using tris-HCl, namely 0.3 mg/ml, 0.15 mg/ml and 0.075 mg/ml and their effects on the RBCs in blood samples were studied using optical microscope. Various morphological changes like haemagglutination, shrinking, swelling, distortions, granulation of the membrane and bursting of the cells were observed. The degree of occurrence of a certain morphological change on a particular blood type varied with a variation in its concentration. Also, the same concentration of the extract showed different morphological changes with different blood groups indicating that the blood type is also important in the effects shown by the cell membranes. The crude leaf extracts of medicinal plants significantly affected the integrity and thus, the morphology of the RBCs.