The object of research was to study the behaviour and phenotypic variability of 10 Medicago arborea populations of different origin (4 from Greece, 3 from southern Italy, 2 from Algeria and 1 from France) in a representative area of the hilly Sicilian inland with meanly 500 mm of rainfall per year on a degradated clayey soil. During the period of study (1991/92), within each population 100 plants were observed. A wide variability among the populations and within each population was ascertained for phenological (stages of beginning and end of flowering, of first visible pod and of first mature pod), morphological (leafiness, plant height, diameter and volume) and productive characters (pod and seed yield). The diameter to height ratio appeared to be a particularly interesting trait for the characterization of the populations. The study of correlations among the observed characters showed that pod production is correlated, positively to mean diameter, volume, leafiness and to the duration of flowering and negatively to the beginning of flowering.