Crystallization of isotactic polypropylene in its alpha modification (alpha iPP) can be initiated by a variety of nucleating agents. One of its (010) crystallographic planes is made of a highly symmetrical, lozenge shaped array of methyl groups. So far, this plane was known to interact only with substrates (benzoic acid and its salts, but also polyethylene through its be contact face, and polyamides) with a approximate to 5 Angstrom periodicity which matches a similar approximate to 5 Angstrom periodicity normal to the short diagonal of the lozenge. In the present investigation, this same lozenge-shaped contact face is shown to interact with nucleating agents with periodicities of approximate to 4.2 and approximate to 6.6 Angstrom which match periodicities normal to its long diagonal and to its cell edges, respectively. Three families of nucleating agents with very different periodicities can therefore interact with the same alpha iPP contact plane. (C) 2000 Elsevier Science Ltd. All rights reserved.