By a curve of growth analysis, using photospheric and umbral equivalent widths, published by Fricke and Elsasser, and absolute oscillator-strengths, it has been found, that the gas pressure in a sunspot is lower than in the corresponding layers of the photosphere. Contribution curves have been computed to get more accurate information to which layers of the spot the results relate, which were derived by comparing on the one hand the damping parts and on the other hand the linear parts of the photospheric and umbral curves of growth.