p38 mitogen-activated protein kinase plays a pivotal role in skin inflammation. The purpose of this study was to investigate the role of the various p38 isoforms. p38 beta/delta-knockout-C57BL/6 mice were generated, studied in a 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced skin inflammation model and compared with wild-type mice. The inflammatory response was determined by ear thickness, myeloperoxidase activity and histology. mRNA and protein expression of interleukin (IL)-1 beta and IL-6 was determined by quantitative real-time reverse transcription PCR and enzyme-linked immunoassay. In both groups application of TPA resulted in a significant increase in inflammation, and pretreatment with the p38 alpha/beta inhibitor, SB202190 resulted in a significant inhibition. A significantly slower onset but prolonged duration of the response was seen in p38 beta/delta knockout mice. This was paralleled by a significant, but transient, lower IL-1 beta and IL-6 protein expression in p38 beta/delta knockout mice. Although the p38 alpha isoform is important, our data also demonstrate an important role of the p38 beta and/or delta isoforms in the regulation of TPA-induced skin inflammation.