  We have used the Westerbork Northern Sky Survey (WENSS) to define a sample of
47 low redshift (z < 0.4) giant radio galaxies. This is the largest sample yet
of such radio sources originating from a single survey. We present radio maps
of the newly discovered giants and optical images and spectra of their host
galaxies. We present some of their properties and discuss the selection
effects. We investigate the distribution of the sources in the radio power --
linear size (P-D) diagram, and how these parameters relate to the redshifts of
the sources in our sample. We find a strong drop in the number of sources with
a linear size above 2 Mpc. We argue that this is not a result of selection
effects, but that it indicates either a strong luminosity evolution of radio
sources of such a size, or that a large fraction of radio sources `switch off'
before they are able to grow to a size of 2 Mpc.
