Detachment of adherent targets from their substratum is a unique activity of both CD8+ and CD4+ T cells. Recently, we have demonstrated that with mixed, alloreactive populations, CD4+ T-cell-mediated detachment is kinetically distinct from lysis and requires protein synthesis. Heterogeneity of effector phenotypes precluded further elucidation of the mechanism of detachment at the mixed population level. Here, we examine further the mechanism of target cell detachment by CD4+ cells using clones which differ in lytic efficiency and demonstrate that detachment of adherent targets from their substratum (1) may result from either protein synthesis-dependent or -independent pathways, which can be correlated with differences in clonal lytic phenotype, (2) is contact dependent and does not involve soluble factors, (3) can be pharmacologically uncoupled from IL4 production, as a measure of cytokine release, and (4) fails to correlate with perforin expression by immunocytochemistry. Finally, isolated granule preparations are unable to mediate detachment independent from lysis.