Phosphodiesterase 4 (PDE4) inhibitors negatively modulate many infl ammatory responses, and some of these pharmacological effects are mediated by inhibition of PDE4B in infl ammatory cells. While inactivation of PDE4B, but not other PDE4 isotypes, is known to inhibit lipopolysaccharide (LPS)-induced tumor necrosis factor-α (TNF-α) production in macrophages, a cell type critical in mediating innate immunity, the impact of PDE4B on many other infl ammatory responses in these cells remains largely unknown. Materials and Methods: To investigate whether PDE4B regulates additional infl ammatory mediators other than TNF-α, in this study we initially used two-dimensional gel electrophoresis approach to screen the secreted proteins that are modulated by the PDE4 inhibitor rolipram in LPS-stimulated Raw 264.7 macrophages. Results: Three proteins were identifi ed, of which the proinfl ammatory chemokine CC chemokine ligand 3 (CCL3) and cytokine TNF-α were downregulated and the antiinfl ammatory cytokine interleukin-1 receptor antagonist was upregulated. Further analysis on CCL3 production in mouse peritoneal macrophages revealed that the reduced CCL3 secretion was associated with a substantial decrease in CCL3 mRNA accumulation. The inhibitory effect of rolipram on CCL3 production was mimicked by the protein kinase A activator 6-Bnz-cAMP, but not the exchange protein directly activated by cAMP activator 8-pCPT-2’-O-Me-cAMP. Analysis of PDE4-defi cient macrophages showed that ablation of only PDE4B reproduced the rolipram effect on CCL3 production. Moreover, PDE4 inhibitor potentially attenuates T-cell migration to CCL3 in infl ammatory sites. Conclusions: These fi ndings suggest that PDE4B may regulate the production of diverse infl ammatory mediators in LPS-stimulated macrophages, and an inhibitor with PDE4B selectivity should retain the anti-infl ammatory effects of nonselective PDE4 inhibitors in endotoxin-induced infl ammatory conditions.