Our objective was to evaluate the levels of interleukin-6 (IL-6), soluble receptors of IL-2 (sIL-2R), IL-10, and IL-1 receptor antagonists (IL-1ra) in the serum of patients with psoriatic arthritis (PsA) and to assess the correlation between these levels and parameters of clinical activity of skin and joint disease. In total, 34 patients with PsA and ten healthy volunteers participated in the study. Assessment of joint disease included duration of morning stiffness, number of tender and swollen joints, right and left grip, the presence of inflammatory spinal back pain, and Schober test. Current severity of skin disease was graded according to the psoriasis area and severity index (PASI). Erythrocyte sedimentation rate (ESR) was determined as a marker of disease activity. Serum levels of IL-6, sIL-2R, IL-1ra, and IL-10 were measured by an enzyme immunoassay kit. Significantly higher serum levels of IL-6, sIL-2R, IL-1ra, and IL-10 were found in patients with PsA in comparison with healthy volunteers. A statistically significant correlation was found between levels of sIL-2R and PASI, whereas no association was found with clinical parameters of joint severity. Levels of IL-lra correlated with the number of tender and swollen joints. No correlation was found between levels of IL-6, IL-10, and clinical parameters of skin and joint severity. In the group of patients with PsA, serum levels of sIL-2R clearly correlated with severity of skin disease, whereas levels of IL-1ra were associated with joint severity.