Low winter temperatures in Mediterranean rangelands delay the growth of forage plants, particularly that of Australian cultivars of annual Medicago species (medicks). Finding appropriate associations of medick - Sinorhizobium able to grow at low temperatures is agronomically and economically important. In this context, the performance (plant development, yield and nitrogen fixation) of three Medicago cultivars originating from the Maghreb and the Mashreq were studied in the field at the ICARDA Research Station (Aleppo, Syria) in 1998 and 1999 : M. aculeata accession 80 (A) and accession 5099 (B) and M. rigidula accession 716 (R), with three different sources of nitrogen : N : fertilized ; I : inoculated with strains M620, M508 and BZI of Sinorhizobium meliloti ; and T, control (no inoculation, no fertilization). Results indicate a genotypic variation of the annual medicks in tolerance to low temperatures. Accession A had a slow growth pattern with low dry matter production compared with B and R over the two seasons. In both seasons and at the early growth stages, the Sinorhizobium strain played a key role in plant growth ; both inoculated and fertilized plants of accession R had comparable dry matter yields. The proportion of nitrogen derived from fixation in A was very low, which was reflected, in turn, in the total amount of fixed nitrogen. The proportion of fixed nitrogen in the association R-BZI association was high in both years, where it reached 72 and 87% of the total plant N respectively. It is suggested that associations differed in their response to low winter temperatures. M. rigidula accession 716 inoculated with the strain BZI proved the best adapted association to the local environment among those studied. M. aculeata accession 5099 seemed also promising for winter growth, provided it is inoculated with a strain better adapted to low temperatures.