The nonlinear transmittance of a novel hyperbranched conjugated polymer named DMA-HPV has been measured in CHCl3 solution using a nanosecond optical parametric oscillator. DMA-HPV shows excellent optical limiting performance in the visible region from 490 to 610 nm. An explanation based on the combination of two-photon absorption and reverse saturable absorption was proposed for its huge and broadband nonlinear optical absorption. (C) 2004 Elsevier B.V. All rights reserved.