Some astrological hypotheses related to predisposition to severe mental illness were tested by analysing the zodiacal signs, the interactions between planetary qualities (aspects), and the occurrence of full and new moon dates, on the dates of birth of 221 schizophrenics, compared with 112 normal subjects. The sun signs of the schizophrenics were significantly more likely to be in the signs associated with introversion, while those of the control population were significantly more likely to be in the outgoing signs. A significantly higher proportion of schizophrenics had their Mars (i.e., symbol of aggressiveness) in the outgoing signs than the normal population. A significantly higher proportion of control subjects fulfilled operational criteria for adequacy of number of aspects between the sun and the other planets. The tendency for a higher proportion of schizophrenics to have “difficult” aspects just failed to reach significance. A significantly higher proportion of control subjects had aspects between the sun and mars; and also a significantly higher proportion of control subjects had “soft” (helpful) aspects between the sun and mars. These findings are in keeping with the well-known oddity of schizophrenia (schiz = split; phren = mind); such that, a group which collectively is characterised by an “introverted” self (i.e. sun sign), has a coexisting aggressive tendency (i.e. strong mars) and poor integration between the elements of the psyche and the self (i.e. inadequacy of aspects between Sun and other planets). However, the findings give only partial support to key astrological postulates because there was a non-significant trend for more schizophrenics to be born in “water” signs and on full moon dates.