Transmittance spectra of isolated plant cuticles were measured in the wavelength range from 270 to 600 nm. The cuticles were enzymatieally isolated from the leaves of 27 species (26 evergreen or deciduous woody, one succulent herhaceous) and from four species of fruits. With the exception of subtropical and tropical species all plants were cultivated in the field. The cuticles of the species studied strongly attenuated ultraviolet (UV) radiation at wavelengths < 400 nm while they were practically translucent in the visible range. Relatively broad transmittance minima occurred at wavelengths from 280 to 320 nm (UV-B). Spectral transmittances at 300 nm ranged from 0-004 (Hex aquifoliuin) to 0-50 (Primus avium) for leaf cuticles and from 0-00023 (Cydoitia obtonga) to 0-005 (Matus domeslica) for fruit cuticles. The constitutive UV protection by cuticular pigments may be supplemented, to varying degrees, by pigments located in the epidermal cell wall and protoplast. Thus, it is concluded that only a small fraction of incident UV-B radiation may actually reach the sensitive tissues of the leaves of non-herbaceous species and of fruits.