To the Editor: We thank Dr. Pearson Murphy for her comments on our recent article on neuroactive steroids in patients with panic disorder before and during paroxetine treatment. Because our article was published as a Brief Report, we had to be as brief as possible with regard to the description of our methods. Two of the seven women in both groups were postmenopausal. We agree that the reported progesterone levels of about 20 nmol/liter are too high for this study group, and we therefore have reanalyzed our gas chromatography/mass spectrometry data. In doing so, we found that when switching from steroid analysis by gas chromatography/mass spectrometry from the electron impact mode that was employed in our previous study of depression (1998) to the negative chemical ionization mode, we made a mistake with the calculation of progesterone concentrations. In our article, we reported on calculations based on m/z 178 and m/z 197, which represent both progesterone and pregnenolone (which partially coelute), instead of m/z 197, which represents progesterone only. This explains why the progesterone values reported were too high. We now have recalculated the progesterone levels using m/z 197. The corrected mean progesterone concentrations were 2.9 nmol/liter (SD=0.2) for the comparison subjects and 3.1 nmol/liter (SD=0.2) for the patients with panic disorder before paroxetine treatment. During paroxetine treatment of the patients with panic disorder, progesterone concentrations were between 2.6 nmol/liter (SD=0.2) and 2.9 nmol/liter (SD=0.3). The other steroid concentrations reported are correct. We seriously apologize for this error and thank Dr. Pearson Murphy for bringing up this issue, which enables us to provide the correct progesterone data. The slight differences between the correct progesterone data and those reported in our previous article regarding depression (1998) are probably due to the fact that in the meantime we changed both our gas chromatography/mass spectrometry instrument and our mode of steroid analysis.