Primary central nervous system lymphoma (PCNSL) is a relatively uncommon disease in which spontaneous remission is exceedingly rare. We are reporting three cases of primary CNS lymphoma with spontaneous regression in two to eight weeks, from the time of the initial diagnosis. The remission lasted for four years in the first case, two years in the second, and one year in the third case. Tissue diagnosis was made in the first two cases after relapse, and in the third case a biopsy was done at the initial presentation. The literature and the possible pathophysiological mechanisms of this interesting phenomenon are discussed.