The WAIS-R measurement of IQ in schizophrenic patients is problematic: the Quick Test of Ammons and Ammons has been used as an alternative despite variability in the accuracy of its estimation of IQ in other groups. We have updated the Quick Test and compared our new version with the original in 44 schizophrenic patients, and both versions with the WAIS-R in a subgroup of 15 patients. Improving the Quick Test materials led to improvement in performance independent of long-term memory function: both versions overestimated WAISR IQ. A previous finding of very high correlation between WAIS-R IQ and Quick Test IQ estimate in schizophrenic patients was not replicated. IQ decline measured with the NART and the Quick Test was less than that using the NART and the WAIS-R. We conclude that the Quick Test has serious limitations as an estimate of IQ in schizophrenic patients, and will bias the assessment of IQ decline so that its extent is apparently less than in reality.