Homogeneous nucleation in system containing seed particles is analyzed. The model proposed by the present authors (Kousaka and Nomura, 1997) is applied in the analysis taking additional modification into account where spatial distribution of nuclei is assumed not to be uniform, but random. Experiments, where the diameter and number concentration of seed particles and the generation rate of monomer (precursor) were varied, were performed to verify the analysis. It is found that present analysis can predict well the operating conditions where 1) homogeneous nucleation is predominant, 2) particle growth is predominant and 3) homogenous nucleation and paricle growth coexist.