A small (<1%) component of delayed fluorescence has been observed from the sublimates of pyrene, 3,4-benzpyrene, 3,4-benztetraphene, chrysene and coronene excited by ultra-violet light in vacuo at room temperature. The spectrum of this component is similar to that of the total luminescence emitted at room temperature, but it persists for some milliseconds after excitation cut-off. The failure to observe the delayed fluorescence in the presence of air and the increase in intensity of the delayed component with the state of subdivision of the solid particles indicates that the emission originates at the crystal surface. The decay of the fluorescence in the millisecond region is virtually exponential for 3,4-benzpyrene and 3,4-benztetraphene, but is non-exponential for the other compounds.