This study was conducted to investigate the effects of salt stress on proline, chlorophyll-a, chlorophyll-b, total chlorophyll, carotenoids, sodium, calcium, potassium, chloride (Cl) contents of some onion (Allium cepa L.) cultivars. Seeds of Akgun-12', 'Besirli-77', 'Beyaz Kirmasi, 'Kantartopu-3', 'Metan-88' and 'Texas Early Grano' were germinated in peat material and transferred to plastic pots after 21 days of sowing. The plants have been grown in vermiculite by substrate culture technique. The early plant stage (63 days old plant) was used for screening studies. Three different salinity levels (0-control, 50 mM and 125 mM NaCl) were tested under greenhouse conditions. After six weeks of transferring, leaf parts were isolated and studied for physiological and mineral analyses. Cultivars showed different responses to NaCI. Increased salinity levels resulted in decreased chlorophyll-and carotenoids, increased proline. The sodium (Na+), potassium (K+) and chloride (Cl-) contents of plants were significantly affected by salinity in all cultivars.