mJy level in a 12 hour synthesis observation and can survey a field of one square degree per exposure at 600 MHz ($z_{oh}\approx 2$), would be likely to detect a few objects per field, when it is equipped with a spectrometer capable of 80 MHz (or more) bandwidth.

The luminous quasar population shows a still stronger evolution than is typically suggested for normal galaxies. Since the most luminous OH masers are associated with the most luminous galaxies in the nearby universe, it is reasonable to speculate about a possible relation between hosts for OH maser and quasars and the possibility that both may be driven by mergers and interactions. Figure \[qsoevol.fig\] shows recent observational constraints on the comoving number density of bright QSOs ($M_B<-24.5$ $+5\log(h)$), as presented by Hewett et al (1993) for $z< 2$ and Schmidt et al (1995) for $z>2.5$; these studies provide evidence that the comoving density peaked at $z\approx 2$ to 3. Representative curves for describing the increase in density $\phi_{-24.5}$ with redshift are drawn in the figure and indicate that $\phi_{-24.5}$ is roughly proportional to $(1+z)^6$ to redshift as high as $z\approx 2$. The QSO evolution is often described as an evolution in luminosity; Boyle 