The genetics of salinity tolerance in rice through in vitro study was investigated using six-parent half-diallel. Test materials were two tolerant (CSR-10 and CSR-5), two moderately tolerant (SAR-41 and NDR501), and two sensitive genotypes (IET12860 and IET11149), and their 15 F₁s. Callus cultures on MS (Murashige and Skoog, 1962) media containing 1.5% salt, were evaluated for callus growth, Na/K ratio, proline content in callus and total regeneration frequency. The tolerant and moderately tolerant genotypes had a higher callus growth and lower Na/K ratio in callus, containing more proline and higher regeneration ability. The sensitive genotypes produced low callus growth and showed no regeneration ability. Na/K ratio and proline content were mainly controlled by dominant genes, while total regeneration and callus growth were controlled by recessive genes. The broad and narrow sense heritabilities were high for all traits. The combining ability analysis demonstrated preponderance of additive gene effect(s) in control of callus growth and regeneration percentage. For the salt tolerance indices –Na/K and proline – both additive and non-additive gene interactions were found important. The tolerant and moderately tolerant parents were good general combiners for all traits, and produced best combinations. A highly significant negative correlation between callus growth and Na/K ratio, and significant positive relationship of callus growth with proline content, and total regeneration potential was observed.