Over thirty-five years have elapsed since Dr Joshua Bierer opened the first psychiatric day unit in London in 1946. Following a somewhat tentative start in the early 1950s, day hospitals expanded rapidly during the latter 1950s, ‘60s and into the ‘70s, and are now regarded as an established part of the psychiatric services. However, it is probably a truism that many of the staff working in psychiatry know little more about the philosophy, practice and effectiveness of day care than their colleagues did a generation ago.