  There has been some disagreement about the strength of evolution exhibited by
IRAS galaxies. With a parameterisation such that the co-moving density
increases as $(1+z)^P$ measurements of $P$ range from $2\pm3$ to $6.7\pm2.3$.
We have recently completed a deep IRAS redshift survey which should help to
clarify the situation. Paying particular attention to possible systematic
effects (notably Malmquist Bias) we claim positive detection of evolution
within this sample at the $3\sigma$ level. Our best estimate of the strength of
evolution seen in this survey is $P=5.6\pm1.6\pm0.7$ corresponding to
luminosity evolution $L(z)=L_{z=0}(1+z) ^{3.3\pm0.8\pm0.6}$. This estimate is
consistent with all previous determinations of the rate of cosmological
evolution of IRAS galaxies. Neither this survey nor any previous survey is
sufficiently deep to distinguish between pure luminosity and pure density
evolution nor between different parameterisation of these forms.
