Quantitative versions of three models of fixation-duration frequency distributions are presented: those proposed by Suppes (1989), McConkie, Kerr and Dyre (1994) and a modified version of that proposed by Harris, Hainline, Abramov, Lemerise and Camenzuli (1988). These, plus two additional versions of the Harris et al. model, were fit to a large set of eye-movement data from a group of adult readers. The McConkie et al. model fit the data best, though the fit appears to result primarily from the functions used rather than from the architecture proposed.