Tris-2,3-dimethyl-hexylamide of trimesic acid (TATA) is an new type of beta-nucleating agent for isotactic polypropylene (iPP). The crystallization, melting characteristics, and the supermolecular structure of iPP nucleated with TATA were studied on the samples crystallized under nonisothermal and isothermal conditions. The b-nucleating ability of TATA was rather high even at low concentration. It was established that TATA possessed dual nucleating ability generating samples with mixed (alpha and beta) polymorphic compositions. The beta-content showed an maximum value at low concentrations (10-100 ppm) of TATA. The beta-content decreased with increasing concentration of TATA in the higher concentration range. The highest beta-content (about 80%) was achieved at the crystallization temperature T(c) = 110-120 degrees C at low concentration of TATA. The crystallization curves registered at constant cooling rate or under isothermal condition have a single peak in spite of the formation of two polymorphic modifications. The crystallization isotherms cannot be linearized according to the Avrami equation because of simultaneous crystallization of the alpha- and beta-forms, having different nucleation and growth rate. It was also found that the beta-content increased with increasing conversion during isothermal crystallization because of the higher growth rate of the beta-phase. The beta-phase formed in the presence of TATA consist of lamellar crystallites. In the early stage of the crystallization, hedritic structure is formed. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 1469-1480, 2011