Twelve variants of four inbred lines, viz., W- 14', -1A1F-9', 'HY' and 'K-55', maintained for several years were crossed with an unrelated synthetic variety, 'No.6', to see the shift in combining ability for yield and yield components. Non-significant differences were found for number of ears per plant, number of kernel rows per ear and number of kernels per row. However, sufficient differences were found among the variants of 'M-14' and 'HY' for number of ears per plant and number of kernel rows per ear. Differences among top crosses of the different versions of the same inbred line were highly significant for kernel weight and grain yield per plant except for 'HY'. Thus, the heritable changes that occurred in these lines not only affected the morphological traits of the line itself but also its combining ability in hybrid combinations.