The diffractive dissociation of virtual photons, \gamma ^*p \rightarrow Xp, has been studied in ep interactions at HERA. The data are presented in terms of the diffractive structure function F₂^D and d\sigma /dM_X. The Pomeron intercepts, extracted from diffractive and inclusive ep interactions, are compared. The Q²variation of the ratio of the diffractive to inclusive cross sections on W, the photon--proton center of mass energy, illuminates the transition from the perturbative, high Q², region to the photoproduction limit. The ranges studied in both W and Q² are extended with respect to previously available results.

PACS numbers: 13.60.Hb, 14.70.--e