The influence of NaCl content in Hoagland medium – in concentrations of 25, 50, 75 mmol dm^-3 – on the growth and photosynthesis of soybean seedlings (cv. Progres and Naviko) was studied. Fresh and dry weights of shoot and root and photosynthesis intensity were determined. It was observed that with increase of NaCl concentration in the medium there is a significant decrease of the fresh and dry weight of the shoot in plants of both cultivars. There was no effect of increased NaCl concentration in the medium on the fresh weight of the roots of the two soybean cultivars. Only in the case of the dry weight of roots a negative effect was noted for Naviko cultivar at NaCl concentration of 75 mmol dm^-3. The higher concentration of NaCl in the medium (75 mmol dm^-3) caused a impairment of CO₂ assimilation of both soybean cultivars. The results showed also that young plants of Progres cultivar more salt stress tolerant than Nawiko cultivar.