Relevance. A concept of the cumulative state of patients is introduced to obtain sufficient samples and reliably assess the clinical situation, establish significant deviations and take clinical measures. Intention . To suggest a diagnostic and prognostic approach based on statistically processed parameters from severely burnt patients. Methodology. The data from 1300 patients treated in 1980–2010 at the clinic of thermal lesions were assessed. The patients were aged (48 ± 12) years and had superficial burns of more than 30 % and deep burns of more than 10 % of the body surface. For data processing, statistical methods including assessment of the distribution of random variables as well as histograms were used. Results and Discussion. Diagnostic parameters are random, thus precluding from unambiguous conclusions on the condition of patients, and should be investigated statistically. Preliminary step of such research is to assess the statistical distribution functions for parameter values. Statistical correlations between parameters can be found only if they are distributed similarly. Studies have shown that magnitudes of most diagnostic parameters are distributed normally. Those deviating from the normal distribution can be explored as normally distributed for large samples. Conclusion. Patients’ condition is a dynamic process and variations of diagnostic parameters are random, i.e. have a noise bias. Therefore, reliable predictions in the course of treatment are impossible. Methods of mathematical statistics help to resolve this problem. Statistical analysis in the treatment of burned is particularly topical and should become a working tool in the practice of diagnosis and prognosis of patients’ condition.