Inflammation present in restenosis after angioplasty is associated with production of cytokines such as tumor necrosis factor (TNFalpha). However, limited data exist on the possible increase in TNFalpha and TNFalpha receptor expression induced during the chronic phase after stenting. To this end, swine underwent balloon denudation (PTCA) and stent implantation in coronary arteries. At day 1, 7 or 28 post-procedure, sections from injured and reference vessel segments were evaluated for extent of pathology and expression of TNFalpha and TNFalpha receptors (RI and RII). Restenosis assessed at days 7 and 28 showed, respectively, two- and six-fold more neointimal (NI) area in stented than in PTCA segments. Unlike reference segments, TNFalpha-positive cells were detected in both the media and the NI of injured segments, with a significant increase over the 28-day time frame. Stenting was associated with an eight-fold enhancement in TNFalpha expression over PTCA. TNFalpha expression and NI area tended to correlate in injured segments. Furthermore, the pattern of expression of TNFalpha-RII, but not TNFalpha-RI, resembled that of TNFalpha itself. These results implicate TNFalpha and TNFalpha-RII as important actors in both the acute and the chronic phases of inflammation following stent implantation.