There are high expectations regarding the use of phosphodiesterase (PDE) IV inhibitors to treat asthma, as indicated by the many pharmaceutical companies that are investing in the development of these agents [see table]. Recently, efforts have been focused on designing PDE IV inhibitors that are better tolerated than the first-generation agents, but that have at least equivalent therapeutic activity. Progress in this field of research was discussed at an IBC conference on ‘Therapeutic Opportunities for Allergic Diseases’ [London, UK; December 1996].