An observational investigation has been carried out on compact galaxies (a category defined by Zwicky) which have been identified on the Palomar Sky Survey. Their colours and spatial distributions are discussed. Results of image tube spectroscopy, made at McDonald Observatory, of 44 compact galaxies are reported. They indicate that the majority, those redder in colour, have conventional stellar spectra, while the bluer objects are of a more diverse nature. Spectra of three red compacts (obtained by Zwicky with the Palomar oo-inch telescope) are compared with spectra of conventional galaxies and it is suggested that the high surface brightness of these compact galaxies may be accounted for by a greater proportion of high luminosity stars.