Polymeric formulations of plant growth regulators (PGR) are high-molecular weight systems in which the PGR unit can be slowly released providing prolonged action and effectiveness in a wide range of concentrations. In this study, Achimene explants were used for testing the biological activity of polymeric derivatives of NAA and 2,4-D. Shoots of Achimenes `Bella', obtained from leaf segments cultured in vitro, were transferred for 8 weeks on Murashige and Skoog (MS) medium supplemented with different levels of conventional or polymeric NAA (0, 0.01, 0.05, 0.1, 0.5, 1.0, 1.5, 2.0, 2.5 mg·liter–1) and 2.4-D (0, 0.01, 0.05, 0.1, 0.5, 1.0, 1.5 mg·liter–1), each combined with three levels of BAP (0, 0.1, 0.5 mg·liter–1). Compared to conventional NAA, twice as many shoots proliferated with higher dry weight, at 0.5 0.1, 1.0, or 1.5 mg·liter–1 polymeric NAA with 0.5 mg·liter–1 BAP. In another trial, the combination of 0.05 or 0.1 mg·liter–1 polymeric 2,4-D with 0.1 BAP gave more shoot and vigorous growth without callus formation, compared to conventional 2.4-D These results suggest that the polymeric derivatives of auxins used in this study enhance regeneration and growth of Achimenes in vitro more effectively than conventional formulations, at greater concentrations, without causing toxic or inhibitory effects.