The tail region of the photocurrent transient observed in the conventional time-of-flight measurements has been experimentally studied as a function of the applied field and sample thickness for amorphous selenium stabilized with 0.2–0.3% As alloying and ∼10 ppm Cl doping (stabilized a-Se). The stabilized a-Se films used in the present study were typical x-ray photoconductors for use in x-ray imaging with a detector thickness in the range of 133–425 μm. Dispersions arising from the mutual Coulombic repulsion of charge carriers was found to give a noticable contribution to the total spread of the carrier packet even at relatively low injection level and extrapolating this function to zero injected charge. The hole transit time dispersion, Δt_TOF, reveals a power law electric field (F) dependence of the form Δt_TOF ∼ F⁻ⁿ where n ≈ 1. It is shown that the observed dispersion cannot be interpreted on the basis of the multiple-trapping model nor conventional diffusion while the concept of charge carrier transport within a random potential landscape allows one to explain the observed field dependence of the hole photocurrent transients in terms of a Gaussian distribution of the effective carrier drift mobilities in which the normalized mobility spread Δμ/μ is 0.083 – 0.042.