Abstract: Obesity and diabetes have led consumers to increasingly seek out products containing low-calorie sweeteners. In this context, the intense sweeteners, especially plant proteins that interact with the taste receptors, are playing a growing role. Among the sweet-tasting proteins thaumatin seems the most promising. Production of thaumatin by transgenic plants might be an interesting alternative to the extraction of this product from the natural source. Another possible application of the unusual properties of thaumatin is to produce transgenic plants containing a protein capable of inducing a sweet taste phenotype. The taste of 5 crop species, cucumber, pear, potato, strawberry, and tomato, was improved by expressing the thaumatin II gene under control of the 35S promoter. Only in the case of transgenic cucumber were sensory assessments carried out for several cultivation cycles. Also, processed fruits of transgenic cucumber, as well as fresh-cut transgenic cucumber salads, were the subject of sensory analysis. Transgenic cucumber expression of the thaumatin II gene resulted not only in sweeter taste, in comparison with the control, but also in higher aroma acceptability. Therefore, the authors of this article have summarized sensory properties of transgenic crops expressing the thaumatin II gene, placing special emphasis on the sensory characteristics of transgenic cucumber. Consumers often perceive disparagingly food deriving from genetically modified (GM) plants, partly because of some concerns about unintended effects. To address such concerns, this article also summarizes the food safety evaluation of transgenic crops expressing the thaumatin II gene. Future research directions are suggested.