Cliffs of the Niagara Escarpment, Ontario, Canada have been fragmented by glaciation and human activity into fragments of different sizes. To determine if the number of lichen and plant species (species richness) responds to natural variation in fragment area, I sampled species richness and frequency on 21 cliff fragments and analyzed the data using regression analysis. Moss and vascular plant richness per unit area was not significantly different between large and small cliff fragments while lichen richness increased slightly. The best regression models relating species richness to fragment characteristics were not simple exponential species-area models. Except for lichens, the best fitting linear species-area models had slopes that were not significantly different from zero. There was no difference between the slopes of species-area curves for large contiguous cliff faces and for fragments. Thus, neither area nor fragmentation appeared to affect species richness on cliff fragments.