Analytical data from the characterization of the liquid products from the thermal cracking of n-C-7 Cold Lake asphaltenes were transformed to probability density functions (PDFs) that described the molecular weight distributions of the asphaltene building blocks. These distributions were used for Monte Carlo construction of populations of 10 000 asphaltene molecules, constrained by an experimental molecular weight distribution and the yield of products boiling below 538 degrees C from cracking in the presence of hydrogen and iron sulfide. The resulting distribution of asphaltene molecules contained between 1 and 15 building blocks, with a mode of 4. The mode of the distribution was insensitive to the fraction of the asphaltenes that consisted of large building blocks, boiling above 538 degrees C. Breakage of the bonds between the building blocks, to simulate cracking, gave yields of product fractions and boiling curves that were consistent with the experimental data. The relatively small number of building blocks in the majority of the asphaltene molecules suggests that molecular topology is not significant in the cracking reactions. Simulation of the cracking reactions linear versus dendritic molecular topology did not show significant differences in yield of product fractions.