The invasive behaviour of 8 lymphoma cell lines were tested by an in vitro monolayer invasion assay. The metastatic cell lines (TAM 4D1.2, DCH10Sp, TAM 4D6.2, E4 and BWLi) were more invasive than their non-metastatic counterparts (TAS 5C4, BWO and DCH 10). There was a positive correlation between their invasiveness and the PGE1- and forskolin stimulated cellular cAMP levels. Invasiveness and basal cAMP levels could not be correlated. Pretreatment with pertussis toxin (50 ng/ml) for 24 hours provoked did not significantly affect the basal and PGE1-stimulated cAMP levels in all cells. Yet, the toxin catalysed the ADP-ribosylation of 40 kDa components in all cells and provoked a significant increase in the invasiveness of non-metastatic cell lines and a decrease in the invasiveness of metastatic cell lines. These data suggest that the invasiveness of T-lymphoma cell lines might be controlled by a complex interplay between different signal transducing pathways in the membrane, rather than by the intracellular level of cAMP.