The present paper aim to answer following questions: 1. What is serum beta-2-M levels in HTP? 2. Does significant correlations between serum beta-2-M levels and serum creatinine levels or creatinine clearance (inulin clearance) exit? 3. Does any significant correlation between serum beta-2-M levels and blood cyclosporine A concentration exit? Three groups of subjects were studied. The first group consisted of 33 heart transplant patients (HTP), the second group consisted of 12 patients with small decline kidney function, and the third one consisted of 36 healthy subjects. In all examined subjects serum beta-2-M (RIA) creatinine, creatinine and inulin (steady state dosis method) clearance were assessed. CONCLUSIONS 1. In observed HTP serum beta-2-M level is significantly higher then in controls and patients with small decline kidney function; 2. A significant correlation between kidney function and -2-M level in HTP as well as in other examined groups subjects exit; 3. Presence a significant positive correlation between serum beta-2-M level and blood cyclosporine A concentration suggest that beta-2-M level can be a good parametr to define cyclosporine A tubular toxicity.