In this paper we demonstrate that the generation of cytotoxic T-cell hybridomas (CTH) that retain classically H-2 restricted and antigen-specific lytic activity is not generally feasible by fusion of cytotoxic T cells (CTL) with the AKR thymoma BW5147. However, CTH that express a nonspecific lytic activity are readily generated, as revealed by lectin-dependent assays. We analyse several such hybridomas for the nature of their lytic activity and for the expression of various function-associated T-cell molecules. We show that the lytic activity retained by CTH is atypical in that only P815 mastocytoma cells, and no other tumour targets, are lysed in the presence of phytohaemagglutinin (PHA). However, in other respects this lytic activity resembles that of normal CTL: it requires cellular contact, results in a reduction of the viability of the target cells, and is sensitive to both EDTA and low temperature. Lytic CTH express low amounts of T-cell antigen receptor (TCR), whereas non-lytic CTH have no detectable TCR on their surface. Most CTH, lytic or non-lytic, fail to express Lyt 2. We conclude that the loss of antigen specificity in CTH is due to reduced expression of T-cell antigen receptor as well as of other functionally relevant molecules. We further conclude from this work that a search for a better fusion partner may be indicated to facilitate the reliable production of cytotoxic T-cell hybridomas.