  We investigate the distribution of mass M and orbital period P of extra-solar
planets, taking account of selection effects due to the limited velocity
precision and duration of existing surveys. We fit the data on 63 planets to a
power-law distribution of the form dn=CM^{-alpha}P^{-beta}(dM/M)(dP/P), and
find alpha=0.12+-0.10, beta=-0.26+-0.06 for M<10M_J, where M_J is the Jupiter
mass. The correlation coefficient between these two exponents is -0.32,
indicating that uncertainties in the two distributions are coupled. We estimate
that 3% of solar-type stars have companions in the range 1M_J<M<10M_J,
2d<P<10yr.
