Cellular responses of two rapid‐cyclingBrassica species. B. napusandB. carinata, to seawater salinity were characterized to determine whether callus showed a tolerance similar to that of whole plants. Callus was initiated from the leaves of 7‐day‐old seedlings ofB. napusandB.carinataand then subcultured with two different levels of seawater salinity (2.3 and 5.2 g l−1Instant Ocean. Aquarium Systems, Inc. Mentor. OH, USA) for 14 days. Callus growth of both species was reduced by seawater salinity. Based on the percentage of the reduction in the relative fresh weight gain.B. napuswas more salt‐tolerant thanB. carinata. consistent with the response of whole plants of the same species to seawater salinity. Seawater salinity caused changes in the concentrations of Na, K. Ca, Mg and Cl in bothB. napusand B.carinata. The growth expressed as the percentage of control was significantly (P = 0.05) positively correlated with the concentration of Ca. and K/Na and Ca/Na ratios. It was also negatively correlated (P= 0.01) with the concentrations of Na. Cl and Mg. In comparison withB. carinala. the salt‐tolerant species,B.napus, showed a small reduction in the concentrations of Ca and K in the salt‐stressed plants relative t