The effect of biomaterial topography on healing in vivo and monocyte/macrophage stimulation in vitro was assessed. A series of expanded polytetrafluoroethylene (ePTFE) materials were characterized by increasing average intranodal distance of 1.2 μm (1.2-ePTFE), 3.0 μm (3.0-ePTFE), and 4.4 μm (4.4-ePTFE), but presented consistent surface chemistry with nonporous PTFE (np-PTFE). Subcutaneous implantation of 4.4-ePTFE into mice resulted in a statistically thinner capsule that appeared less organized and less dense than the np-PTFE response. In vitro, isolated monocytes/macrophages cultured on np-PTFE produced low levels of interleukin 1-beta (IL-1β), 1.2-ePTFE and 3.0-ePTFE stimulated intermediate levels, and 4.4-ePTFE stimulated a 15-fold increase over np-PTFE. Analysis of cDNA microarrays demonstrated that additional proinflammatory cytokines and chemokines, including IL-1β, interleukin 6, tumor necrosis factor alpha, monocyte chemotactic protein 1, and macrophage inflammatory protein 1-beta, were expressed at higher levels by monocytes/macrophages cultured on 4.4-ePTFE at 4 and 24 h, respectively. Expression ratios for several genes were quantified by RT-PCR and were consistent with those from the cDNA array results. These results demonstrate the effect of biomaterial topography on early proinflammatory cytokine production and gene transcription by monocytes/macrophages in vitro and decreased fibrous capsule thickness in vivo.