A detailed theoretical analysis of aerosol nucleation and growth in laminar flow, including the important aspects of mass and energy transfer and aerosol size distribution dynamics, is presented. Simulations of dibutyl phthalate aerosol formation and growth in a laminar flow cooled tube, in the presence and absence of seed particles, are carried out using the classical and Lothe-Pound theories of homogeneous nucleation. The competition between new particle formation and vapor growth onto seed particles is explored in detail. The mathematical model is compared to experimental measurements of aerosol volume distribution and dibutyl phthalate mass balance for a laminar flow cooled tube without seed particles. The model with Lothe-Pound theory shows fair agreement with the mass balance data, but over-predicts the total aerosol number concentration by four orders of magnitude.