2-chlorodeoxyadenosine (2-CdA) is a new purine analogue which has shown great efficacy in the treatment of hairy cell leukemia. Only one case of cutaneous reaction after this treatment has previously been reported. The data from 33 patients treated with 2-CdA were retrospectively reviewed. Seven of these (21%) developed a disseminated eruption during the month following 2-CdA. One had toxic epidermal necrolysis. A reaction to the associated antibiotic therapy seemed "likely" or "very likely" in 5 out of the 7 cases. The incidence of adverse drug reactions may be increased after 2-CdA, and the role of CD4+ lymphocytopenia in these reactions is discussed.