A model for the chemical evolution of a disk galaxy is presented. The model reproduces all the basic
parameters of our own Galaxy, including, for the first time, the correlation between metallicity and height above
the Galactic plane. One version of this model had been used earlier to study the effect of heavy element loss
from spiral galaxies on the chemical evolution of the intergalactic medium. Here, the primary emphasis is on
investigations of the star formation history. Varying the basic parameters of the model -- the mass and radius of
the galaxy¨and incorporating a delay in the onset of star formation make it possible to model different scenar-
ios for the evolution of a galaxy's luminosity. There is a phase of enhanced star formation in the early stages of
evolution of massive galaxies. Taking into account the absorption of optical radiation by dust grains makes
it possible to explain certain observed characteristics of the luminosity evolution, in particular, the absence
of bursts in optical luminosity in disk galaxies at the initial period of intense star formation. The possibility
of reconstructing the star-formation history and galactic luminosity from observations of galaxies at different
redshifts z is discussed. If selection effects are accurately taken into account, the model makes it possible to
construct specific evolutionary scenarios that are consistent with the observations. Factors responsible for the
deviation of the evolution of the average luminosity from the luminosity history in individual galaxies are