Abstract: This paper presents a random-fuzzy method for the treatment of the experimental data of mechanical parameters of rock samples. The uncertainty of mechanical parameters of rock samples is discussed. The fundamentals of fuzzy sets are used to derive the random-fuzzy statistics formulae for calculating the numerical characteristics of the experimental data of rock samples. The random statistics formulae are proved to be a special case of the presented formulae. Results shown that the proposed method is more realistic and better than the conventional one.