The protective effects of disodium cromoglycate (DSCG) and beclomethasone dipropionate (BDA) on the late nasal mucosa response to allergen challenge (LNR) were investigated in 42 patients with allergic rhinitis. The 42 patients, selected from a group of 370 patients, developed a total of 52 later nasal responses (LNR), 13 of which were isolated later responses (ILNR) and 29 of which were dual responses (DNR), i.e., where the later response (DLNR) has been preceded by an immediate response (INR). Significant protective effects on the immediate and on the late nasal mucosa responses were seen following the use of DSCG. The late response, being a part of the dual response was decreased by DSCG to a higher degree than the isolated late response. Although BDA also decreased the late response, the isolated late response was decreased to a greater degree than that demonstrated as a part of the dual response. The immediate response was not influenced by BDA at all. It is suggested that DSCG should be used as a drug of first choice to control the allergic rhinitis symptoms. However, in the presence of the later nasal response, BDA should be added, at least at the beginning of the treatment and during the period of peak exposure to allergen, i.e., the pollen season.