  We mapped 12 massive protostellar candidates in the CO J=2-1 line, which in
combination with Zhang et al. (2005) completes an unbiased survey of outflows
for all 48 sources with l>50^o in a sample of 101 massive protostellar
candidates. We detected outflows in 10 sources, implying 88% occurrence
frequency of outflows for the 48 sources. This supports the conclusion of
previous studies that bipolar outflows are an integral component in the
formation process of massive stars. The vast majority of the observed outflows
are much more massive (>10~Mo) and energetic (>100~Mo~km/s) than outflows from
low-mass protostars. They also have large mass outflow rates
(>2x10^{-4}~Mo/yr), suggesting large (~1x10^{-4}~Mo/yr) accretion rates
sufficient to overcome radiation pressure of the central massive protostars. We
compared the frequency distribution of collimation factors of 40 massive
outflows including those of this study with that of 36 low-mass outflows from
the literature, and found NO significant difference between the two. All these
results are consistent with the suggestion that massive stars form through
accretion as do low-mass stars but with much higher accretion rates.
