Objectives: Assessment of gustatory function is a central part of the diagnosis of patients with chemosensory dysfunctions. The taste of monosodium glutamate was described as umami taste a century ago by Ikeda. The aim of this study was to extend a validated gustatory test with 4 concentrations of monosodium glutamate. Methods: The investigation included 96 subjects who reported having a normal sense of taste and smell. Taste function was assessed by 4 concentrations of sweet, sour, salty, bitter, and umami tastes (extended version) and compared to results obtained in a control group (n = 139) not presented with umami. In a subgroup of 46 participants, the complete test was repeated within 7 days to obtain retest values. Results: Group comparisons exhibited no differences in taste sensitivity for each of the 4 taste qualities (p > 0.3) and no deviation with regard to the sum of correctly identified tastants (p = 0.81). Test-retest data from the extended version revealed a high correlation of scores (r46 = 0.77; p < 0.001). Conclusions: The results indicate that the extended version of the gustatory test is applicable for experimental and clinical settings.