Abstract: The results of ultrahigh-time-resolution (ΔT ~ 12 s) observations of the B1 Iab supergiant ρ Leo with the 1.25-m telescope at the Crimean Astronomical Station of the SAI MSU are presented. Regular line profile variations with periods of 15–30 min have been revealed. Significant changes in the average line profiles on time intervals of 1–3 days have been detected. Evidence for the existence of short-period line profile variations on time scales of 15–25 min is provided. The nature of the short-period line profile variations is discussed. The possibility of studying the fast variations in the profiles of broad lines (mostly the Balmer hydrogen and He I lines) using low-resolution spectrographs with R=1000{-}2000 at 1–2-m telescopes is pointed out.