Objective - The aim of the work was to study serum concentrations of magnesium, copper, zinc, phosphorus and calcium in individuals with undifferentiated connective tissue dysplasia (uCTD) and joint hypermobility (JH) in an isolated and combined state. Material and methods - the concentrations of magnesium, copper, zinc, phosphorus and calcium were measured by the direct colorimetric method in 55 people with joint hypermobility and in 34 - without hypermobility. Results - There were no significant differences between serum concentrations of microelementsin groups with and without JH. In patients with mild and severe uCTD significant decrease in serum magnesium concentrations was noted (U=2.12, p=0.034 and U=3.7, p=0.012). In patients with isolated JH significant serum zinc concentrationdecrease was revealed compared with the control group (U=3.12, p=0.022). Serum magnesium concentrations were reduced in all patients with uCTD and JH; in the groups with isolated dysplasia and combined pathology, the differences reached the level of statistical significance (U=2.78, p=0.024 and U=3.2, p=0.018). Conclusion - The study revealed significant associations of a decrease in serum magnesium concentrations with the development of uCTD in an isolated and combined with JH state and decrease in serum zinc concentrations with the development of isolated JH.