The laminar flow diffusion chamber technique for experimental homogeneous nucleation rate measurements is presented. In this type of chamber the flow containing vapor is rapidly cooled and critical supersaturations for homogeneous nucleation are obtained. Here the main operation principles as well as data reduction methods are investigated and the results are applied to dibutyl phthalate (DBP) vapor, which works well in this type of chamber. The nucleation rate has to be calculated using the profiles of saturation ratio and temperature, and using a theoretical expression for the nucleation rate. We have used three different nucleation theories when investigating the experimental nucleation rate : classical nucleation theory, self-consistent correction to classical theory, and the Dillmann-Meier theory. According to investigations in this work the determination of nucleation rate is general and rather independent of the theory used, and therefore the results can be considered reliable. The volume inside which the nucleation event is calculated to take place is examined experimentally. The comparison between model calculations of the actual nucleation volume and experiments show reasonable agreement.