We present a study of Ioffe times in deep inelastic electron-proton scattering. We deduce ‘experimental’ Ioffe-time distributions from the small- x HERA data as described by a particular colour-dipole-model fit. We show distributions for three representative γ* p c.m. energies W and various values of the photon virtuality Q 2. These distributions are rather broad for transversely and very narrow for longitudinally polarised virtual photons. The Ioffe times for W = 150 GeV, for example, range from around 103 fm for Q 2 = 1 GeV2 to around 10 fm for Q 2 = 100 GeV2. Based on our results we discuss consequences for the limitations of applicability of the dipole picture.