  We study the long-term light and spectral variations in the He-strong
magnetic chemically peculiar star HD 37776 (V901 Ori) to search for changes of
its 1.5387 d period in 1976-2007. We analyze all published photometric
observations and spectrophotometry in the HeI 4026 A line. The data were
supplmented with 506 new (U)VB observations obtained during the last 2
observing seasons, 66 estimates of HeI equivalent widths on 23 CFHT
spectrograms and 35 of the 6-m Zeeman spectrograms. All the 1895 particular
observations heve been processed simultaneously. We confirm the previously
suspected increase of the period in HD 37776 which is a record-breaking among
CP stars. The mean rate of the period increase during the last 31 years is
0.541+-0.020 s per year. We interpret this ongoing period increase as the
slowing down of the star's surface rotation due to momentum loss through events
and processes in its magnetosphere.
