The delayed S 1 → S 0 fluorescence from the first electronically excited singlet state S 1 of an aromatic compound in liquid solution is caused by diffusion-controlled triplet-triplet annihilation (TTA) T 1 + T 1 S 1 + S 0 . For a random spatial distribution of triplet state molecules at time t=0, Smoluchowski's theory for a diffusion-controlled reaction predicts a time-dependent rate constant k d (t) of TTA with k d (0) k d (∞). If the triplet state is populated by optical excitation S 0 → S 1 and subsequent intersystem crossing S 1 T 1 , it is principally impossible to generate a random distribution of triplet state molecules. Since the pair S 1 T 1 is an intermediate during the creation of a triplet pair T 1 T 1 , Forster energy transfer S 1 + T 1 → S 0 + T n may compete with the generation of T 1 T 1 at short intermolecular distances. As a consequence, one expects an anti-Smoluchowski behavior of TTA with k d (O) k d (∞), or with respect to the intensity of the delayed fluorescence, a strong initial rise. The anti-Smoluchowski behavior of a delayed fluorescence has been observed for the first time (with anthracene in a viscous alkane mixture as solvent). The anti-Smoluchowski behavior can be quantitatively described with a simple kinetic model, which contains only four parameters: the diffusion coefficient of molecules in T 1 , the Forster radius for the S 1 -T 1 energy transfer, and two parameters specifying an exponential distance dependence of the annihilation rate constant for a triplet pair.