To the Editor: Dr. Shuer raises some interesting and important issues with regard to our article. She contends that documentation of the phase of the menstrual cycle is critical in understanding the relationship of gonadal hormones to cognitive abilities because of the variation in hormones throughout a normal menstrual cycle. We agree with this point and know that documentation of the menstrual phase is most readily performed in the healthy, nonpsychiatrically impaired individuals Dr. Shuer has vigorously studied. In contrast, our study was an investigation into treatment-resistant female patients with schizophrenia. As we stated in the article, we found patients and staff to be unreliable in providing exact information regarding menstrual cycles. As is true of many schizophrenia patients, a number of our patients were amenorrheic, which complicates the picture even further. Additionally, because testing could not always correspond to the exact day of blood draws because of patient cooperation or ward logistics, we could not guarantee the exact correspondence of serum levels to day of testing. We dealt with these difficulties by sampling weekly over a 4-week period as an estimate of one menstrual cycle. The mean of a group of observations is the best single representation of those observations. We performed correlations of average serum level, variability, and highest level with level of cognitive functioning; all produced significant results. Despite the impreciseness in our measurement, we detected strong relationships, which would speak more to the robustness of these findings than to their lack of validity.