The area, thickness, and volume of erythrocytes of different types (discocytes, stomatocytes, and echinocytes) from normal subjects and coronary patients were studied by laser interference microscopy. Increase of pH value leading to the stomatocyte-discocyte-echinocyte transformations resulted in a slight decrease of cell volume. In coronary patients, erythrocyte had larger area and volume and exhibited increased aggregation capacity compared to erythrocytes from controls. The results recommend laser interference microscopy as an adequate method for erythrocyte evaluation in laboratory diagnostic measurements.