94 MEFS, MEDITERRANEAN ERYTHROCYTE FILTRATION STUDY ON ESSENTIAL HYPERTENSION. MEFS group of the Mediterranean League on Thromboembolism; S. Coccheri, coordinator, University Hospital S. Orsola, Bologna. Italy. The aims of this multicenter study were: 1) to put up a collaborative exercise in Haemorheology in Mediterranean countries and 2) to contribute to knowledge of rheologic changes in essential hypertension (EH). Erythrocyte filterability, an important haemorheologic parameter, is being investigated in a large number of patients (pt) suffering from EH in a collaborative international study organized by the Mediterranean League on Thromboembolism. To this study 11 groups of workers belonging to 7 different countries participate according to the following protocol. Each group has been requested to study 20 pt of both sexes, whose diastolic blood pressure had been repeatedly found >95 mmHg, under no antihypertensive drug treatment since at least 7 days. Exclusion criteria were:)60 y age, secondary H, diabetes, overt central or peripheral vascular diseases, pregnancy, delivery (within 6 m.), surgical operation (3 m.), inflammatory diseases (2 m.). An equal number of healthy subjects, matched for age and sex, have also been investigated. The haemorheologic tests were: filtration of whole blood (according to Reid and Dormandy), and of washed erythrocytes resuspended in buffer after removal cf WBC through cotton wool. Fibrinogen (immunologic), total fractionated plasma protein pattern and coulter blood counts were also determined. The results are currently being evaluated.