Radiation-induced radical-pair formation has been modeled in a simple atomistic study, utilizing Molecular Simulations Inc., (MSI) amorphous macrocells, containing the three poly(propylene) tacticities; isotactic (i-PP), syndiotactic (s-PP), and atactic (a-PP). For all three tacticities, the ratios of secondary "partner" radical probabilities, generated following hydrogen atom ejection from the primary radical site, were found to deviate only a little from the availability of hydrogen atoms of the PP "a"-, "b"-, and "c"-type carbons (-(CH2CHCH3)-H-a-H-b-H-c-). It is demonstrated that b-type partners have the lowest probability of being formed, and therefore, b-type primary radical initiation is required to produce the ESR spectra generally observed, which is predominantly composed of b-type radicals. It is reasoned that the hydrogen atom on the b-carbon is most easily ejected, either following ion-molecule-electron recombination, or as proton ejection. Radical-pair distance distribution functions demonstrate that most partners are formed on immediately adjacent chains, because ejected hydrogen atoms or protons have little possibility to travel much further. Mean radical-pair distances were found not to differ greatly at rho approximate to 0.90 x 10(3) kg m(-3), being 6.15, 6.20, and 6.26 Angstrom, from b-type radical initiation in i-PP, s-PP, and a-PP, respectively. Density variation had only a small effect on the mean radical-pair distance in i-PP, except when the polymer was completely amorphous, a condition which never occurs in reality. Similarly, only small mean radical-pair distance variations are expected in s-PP and a-PP, over the range of densities normally encountered.