We develop a theory of fluorescence depolarization for a probe molecule reorienting in a mesophase with local uniaxial symmetry and a random distribution of directors tilted with respect to the axis of the structure. The theory should be applicable, e.g., to probes dissolved in a pyramidic liquid crystal or to chromophores attached to a side chain polymer brush. We work out expressions for the polarized fluorescence intensities as a function of the cone opening and show how these depend on the orientational correlation functions and on the order parameters for a uniaxial or biaxial probe. (C) 2002 Elsevier Science B.V. All rights reserved.