A theoretical analysis of the chemical response of the stratosphere to possible long-term variability of solar ultraviolet irradiance has been performed, taking into account the thermal feedback effect on the reaction rates. Numerical values of ultraviolet and visible irradiation fluxes used in this work are given for aeronomic modeling purposes and a possible variability related to the 11-year solar cycle is suggested on the basis of recent and reliable observations of solar ultraviolet irradiance. This variability has been introduced in a stratospheric two-dimensional model which simulates the zonally averaged distribution of the chemical species related to the oxygen, hydrogen, nitrogen and chlorine families. The results lead to a total ozone variation of the order of 3% from the minimum to the maximum solar activity, with a maximum of about 10% in the upper stratosphere. At these heights, the calculated temperature change is close to 2-4 degrees. The N2O concentration appears to be one of the most sensitive to long-term solar variability and a monitoring of this constituent would be useful to give information on the solar variability in the ultraviolet.