Dependence of the population morbidity on the ground-level ozone concentration in the summer of 2010 was studied in a city with low urbanization (Vyatskie Polyany, Kirov oblast) and in Moscow. At a high air temperature and low ozone concentration, the population morbidity was not associated with these parameters in Vyatskie Polyany. When the average daily ground-level ozone concentration exceeded 60 μg/m3 for 13 successive days, the correlation coefficient between ozone concentration and the number of ambulance calls was statistically significant, r = 0.62. Heavy smoke from forest fires reduced ozone concentration, and the number of emergency calls did not increase. In Moscow, the incidence of respiratory diseases and population mortality were growing up at high ozone concentrations.