In an approach that explicitly incorporates genetic changes over consecutive generations of selffertilization, we contrast the effect of different modes of inheritance for selfing rate upon the evolutionary equilibrium selfing rate. A monotonic decline of fitness with consecutive generations of selfing was assumed. We found the range of conditions permitting evolutionarily stable mixedmating systems to increase with the number of genes controlling the selfing rate. When the mating system is controlled by a single locus with alternative alleles for complete selfing or outcrossing, alleles for selfing concentrate in inbred individuals and are exposed to stronger selection than the average inbreeding depression. By contrast, when alleles of small effect control the selfing rate, selfing rates do not vary as much between inbred vs. outcrossed individuals; this results in the broader stability of mixed mating. We also find that, provided selfing is not caused by recessive alleles, low levels of outcrossing can be maintained when the average relative fitness of selfed progeny is above 0.5. This is postulated to be due to a long-term advantage for occasional outcrossing in terms of the restoration of low inbreeding coefficients. The assumption of a monotonic decline in fitness with consecutive generations of selfing is also discussed.