Efforts have been made to detect and characterize individual dislocations, small-angle boundaries and extended (nonequilibrium) lattice vacancies, formed by the annihilation of dislocations, in single crystals of anthracene. Only those dislocations emergent at the basal (OOl) faces may be identified using the dislocation-etch-pit technique; but some information regarding dislocations which glide in the basal plane may be deduced from deformation and cleavage studies. Three distinct kinds of experiments have been carried out on a variety of crystals, the dislocation content of which ranges from 102cm−2(for vapor-grown) to 108cm−2(for deformed melt-grown crystals).