  We present the results of recent long-term BVRcIc photometric monitoring of
the type II Cepheid prototype W Virginis. These new observations, made during
the 2006 and 2007 observing season, represent the longest homogeneous,
multicolor light curve of W Vir to date. The BVRcIc light and color curves show
conclusively that W Vir exhibits modest but detectable cycle-to-cycle
variations, the cause of which appears to be multiperiodicity rather than
nonlinearity. We combined our V-band data with the five available years of
ASAS-3 V-band photometry to obtain a 6.5-year light curve that we then analyzed
to obtain the pulsation spectrum of W Vir. We find a best-fit period P(0) =
17.27134 d; along with this period and its integer harmonics, we clearly detect
two additional periods, P(1) and P(low), that are close to but not exactly
2P(0)/3 and 2P(0), respectively. The former, P(1) = 11.52562 d, we interpret to
be the first overtone mode; the latter, P(low) = 34.59760 d is close to the
beat period of P(0) and P(1), as well as to the value of 2P(0). We interpret
the previously reported but thus far unconfirmed descriptions of alternating
minima as manifestations of this multiperiodicity. Finally, we use the period
derived from the V-band light curve to define a new ephemeris: HJD(max) =
2452758.172 + 17.27134E. The resulting (O-C) diagram using 75 years of data
from 1932 to 2007 yields a period change term for the ephemeris of -9.9 times
10(-7) E^(2), indicating a period decrease.
