We report the all-optical switching effect of photoconductive polymer composites based on poly(vinyl carbazole) (PVK) and azobenzene dyes. The optical switching effects were measured by using 514 nm pump beam and 632.8 nm probe beam. The reversible and repeatable change in the transmittance of the probe beam is attributed to the photoinduced anisotropy due to the photoisomerization of azobenzene dyes. The influencing factors of the optical switching effect, such as the modulation frequency and pump beam intensity, were studied experimentally. The experimental results indicate that, as the modulation frequency increases, the switching response becomes quicker, while as the pump beam power increases, the modulation depth becomes deeper. (C) 2003 Elsevier B.V. All rights reserved.