Abstract: Background and Objective: Aluminium cation toxicity remains to be one of the major abiotic factors limiting barley production not only in Kenya but also other parts of the world where this crop is grown. The study aimed at screening both commonly grown barley varieties as well as the improved barley lines to identify potential varieties that could be used in improving tolerance to aluminium toxicity. Materials and Methods: Thirty two winter and spring adapted genotypes were arranged in a completely randomized design consisting of two Al treatments (0 and 148 μM) and barley genotypes as experimental units replicated 5 times. Five-day old seedlings were subjected to hematoxylin staining with 0.2% hematoxylin solution containing 0.02% potassium iodide. Visual assessment on the intensity of root staining was done on a 1-5 scale with 1 as tolerant and 5 as sensitive to aluminium toxicity. Data on net root length, relative net root growth, percent response, hematoxylin staining intensity were subjected to analysis of variance (ANOVA) on Genstat statistical software release 16.0 VSN International Ltd., at 5% level of significance. Mean response were separated using duncan multiple range test. Results: Winter and spring adapted barley differed significantly in their response to aluminium cation toxicity (p<0.05). Net root length, relative net root growth, percentage response, degree of root staining for spring adapted genotypes expressed more tolerance to aluminium toxicity compared to the winter adapted barley. Irrespective of the adaptation to growth conditions, some genotypes expressed exclusion while others utilized fixation mechanisms of tolerance to aluminium toxicity. Conclusion: In conclusion, a number of barley grown in Kenya were tolerant to aluminium toxicity and the study recommends Fanaka, MALT 1, Aliciana and Grace genotypes for studies aiming at increasing tolerance to aluminium toxicity.