User Experience (UX) is a key factor and an opportunity for improvement in digital interfaces. Traditionally, it has been evaluated retrospectively through surveys and interviews. However, this is not always the optimal approach, as it does not measure UX at the moment of human-machine interaction and is therefore prone to human error due to inaccurate recall. Thus, physiological monitoring is emerging as a promising technique to assess UX during interactions. This paper aims to identify UX case studies carried out with physiological monitoring by means of a Systematic Literature Review (SLR). The results of the 33 UX case studies reviewed show that interest in incorporating physiological technologies in UX studies is growing and expanding into different fields. The electroencephalogram (EEG) was found to be the most used physiological tool, and the most used set of tools was the Galvanic Skin Response (GSR) with the electrocardiogram (ECG). In addition, the average number of participants was obtained depending on the physiological tool used. The research opportunities identified are: 1) the combination of different methods and tools in the assessment of UX, and 2), the validation of a sample size for UX tests performed with physiological monitoring Keywords: User Experience (UX), evaluation, Systematic Literature Review (SLR), physiological monitorization