Measurement of the drift mobility defined as the proportionality constant of the mean velocity (v) to the electric field strength (E) is necessary for understanding of carrier transport. However, it is difficult to obtain v from the time-of-flight transients. Thus the velocity obtained from the transit time has been analyzed instead of the mean velocity. The most common measurement of the mobility (μ_{k_ex}) is obtained from the time derived from the intersection of the asymptotes to the plateau and tail of the transients. Because the long tail of photocurrent transients for molecularly doped polymers indicates anomalous dispersion of carrier transit times, the difference between ν/E and μ_{k_ex} is not negligible. Recently, a theoretical photocurrent transients equation (PTE) has been introduced. Fitting of the PTE to nondispersive transients gives the values of ν and the diffusion coefficient (D) simultaneously. In this article, using the PTE, both the mobility (μ^k_cal), obtained from a kink in the photocurrent transient, and the tail-broadening parameter (W_cal) were derived as functions of ν, D and sample thickness. We have tried to explain the anomalous behavior of μ_{k_ex} and the tail-broaden-ing parameter (W_ex) in order to verify the PTE. The dependences of μ_{k_ex} and W_cal on the electric field and the sample thickness satisfactory agreed with those of μ_{k_ex} and W_ex. These verify the PTE and suggest that fitting of the PTE to photocurrent transients is suitable way to obtain the drift mobility.