Based on a group of 220 deaths from sequelae of burns in 1966-1985 the author calculated from the area of the burns injury (grade II and III). from the period of survival and age of the patients the values of LA50 (lethal area 50), i. e. values, expressed in per cent of the body surface, when half the patients die. In the age group of 15-50-year-old ones the LA50 value was 55%, in the group of 51-60-year-old ones 32%, in the group aged 61-70-years 17%, in the group aged 71-80 years 12% and in those above 80 years 9%. On comparison with LA50 values assessed in the same manner in 133 deaths in 1966-1971 an increase of values was found in particular in young and middle aged patients which deadlined with the advancing age of the affected persons. The revealed increase suggesting a more favourable prognosis of burns is due to better therapy.