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The line profile variability and photometric variability of the O9.5 Vp starHD93521 are examined in order to establish the properties of the non-radialpulsations in this star. Fourier techniques are used to characterize themodulations of the He I 5876, 6678 and H-alpha lines in several spectroscopictime series and to search for variations in a photometric time series. Ourspectroscopic data confirm the existence of two periods of 1.75 and 2.89 hr.The line profiles, especially those affected by emission wings, exhibit alsomodulations on longer time scales, but these are epoch-dependent and changefrom line to line. Unlike previous claims, we find no unambiguous signature ofthe rotational period in our data, nor of a third pulsation period(corresponding to a frequency of 2.66 day$^{-1}$). HD 93521 very likelyexhibits non-radial pulsations with periods of 1.75 and 2.89 hr with $l \simeq8 \pm 1$ and $l \simeq 4 \pm 1$ respectively. No significant signal is found inthe first harmonics of these two periods. The 2.89 hr mode is seen at allepochs and in all lines investigated, while the visibility of the 1.75 hr modeis clearly epoch dependent. Whilst light variations are detected, theirconnection to these periodicities is not straightforward.

Spectroscopic and photometric variability of the O9.5Vp star HD93521