Technical Abstract: Post-flowering drought tolerance is a key trait for increasing the production of sorghum [Sorghum bicolor (L.) Moench] in Mediterranean and semiarid tropical climates. The nonsenescent trait, stay-green, is the most significant criterion for assessing post flowering drought tolerance in sorghum. However, assessment of the stay-green phenotype is dependent on the occurrence of drought stress conditions at specific developmental stages in order to achieve meaningful evaluation. Thus, field-based evaluations, most of which are visual, of stay-green drought tolerance are notoriously difficult to perform and require growing lines in multiple locations across several years to achieve efficient selection for the trait. Here we report and demonstrate that leaf dhurrin [(S)-p-hydroxymandelonitrile-ß-D-glucopyranoside] content from irrigated or dryland sorghum is significantly correlated with the level of post-flowering drought tolerance of sorghum lines previously reported as stay-green. The correlation between leaf dhurrin content and post-flowering drought tolerance provides the first quantitative measure of post-flowering stress tolerance from irrigated or dryland pre-flowering sorghum.