The predictions of our 2-D cloud model with detailed microphysics for June 3, 1992 were compared with observations made on the same day during the field experiment CLEOPATRA on June 3, 1992. Using the observed vertical temperature and humidity distribution and the observed aerosol characteristics as model input, excellent agreement was obtained between the observations and the theoretical predictions. The chemical composition of cloud-and rain water was in good agreement with the observations. In addition it was for the first time possible to verify by observation our predictions that the condensation process produces a sharp cutoff in the aerosol particle size distribution, leading to the formation of a cloud interstitial aerosol consisting of particles smaller than the cutoff radius.