The search for an infective agent linked to cutaneous T-cell lymphoma (CTCL) has also included the human T-cell lymphotropic virus type I (HTLV-I). Using sensitive techniques such as Southern blotting under low stringency conditions of hybridization and polymerase chain reaction (PCR) with primer sets designed to match pol, env and pX sequences of HTLV-I, we have screened lesional skin biopsies of 50 Swiss and German patients suffering from CTCL. No evidence of proviral integration of HTLV-I could be demonstrated in any of our patients. Our results, as well as a review of the literature, indicate that at least for European patients, HTLV-I does not seem to play a role in the aetiology of CTCL.