We present the results of our analysis of a time series of high-resolution spectra of the multiple beta Cephei star lambda Scorpii. The data set has a total time-span of more than 5000 days and includes an intensive monitoring campaign during 8 consecutive nights. We confirm the presence of a dominant frequency f(1) = 4.679410 c d(-1) in the data. We show that the amplitude is variable in time according to the light-time effect in the multiple system. The dominant frequency is identified as a prograde dipole pulsation mode. From modelling of the amplitudes and phases across the profiles we derive pulsational parameters, the inclination angle 70degrees less than or equal to i less than or equal to 90degrees and v sin i similar to 125 km s(-1). From a comparison between theoretically calculated forcing eigenfrequencies induced by the close companion and the eigenfrequencies of the observed oscillation mode we find no tidal enhancement or excitation of the pulsation mode of lambda Scorpii. We find indications for the presence of additional frequencies with low amplitudes.