The K giant Arcturus (alpha Boo) was observed with the Birmingham double magneto-optical filter spectrometer using the GHRIL facility at the Nasmyth focus of the 4.2 m William Herschel Telescope of the Observatorio del Roque de los Muchachos in 1988 April to May. Approximately 80 hr of data were obtained over a 2 week interval. Analysis of the data shows the presence of the large (200 m/sec) amplitude velocity variation reported earlier by other observers. However, this more extensive data set strongly suggests that this variation is not singly periodic, as was previously indicated. The nature of this variation, and the implications for stellar seismology, are considered.