The short-time scale spectroscopic variability of some Be stars has been mvestigated with an optical fiber spectrograph and a CCD camera. We have found on time-scale of hours and days: -1) weak changes in the Hα emission line profile of yCas; -2) changes in the structure and the intensity of the Hα emission line core and sometimes in the wings of the Hel λ 6678 of φPer; -3) no table variations in the Hel photospheric line profile λ 6678 and in the core of the Hα absorption line of o And, which do not seem correlated with the photometric period 1.57 days given by Harmanec (1984).