A series of comparative trials on nine popular and pharmacologically distinct regimens for the treatment of hay fever was undertaken in the course of normal general practice in the pollen seasons of 1981-83. One hundred and forty doctors recruited 640 patients to assess the overall usefulness of the treatments on daily diaries. ;Usefulness' was scored on a linear analogue scale weighing up the degree of hay fever symptoms during treatment, side effects and ease of use of the preparation.The regimen with the highest overall usefulness score was beclomethasone diproprionate with sodium cromoglycate eye drops (Beconase and Opticrom). Although the score was not significantly higher than those for methylprednisolone acetate (Depo-Medrone), astemizole (Hismanal) or terfenadine (Triludan), Beconase/Opticrom scored significantly better than mequitazine (Primalan), chlorpheniramine maleate (Piriton), sodium cromoglycate nasal insufflation with xylometazoline/antazoline eye drops (Rynacrom and Otrivine-Antistin) and azatadine maleate (Optimine). Beconase/Opticrom was first in rank order with respect to all the other regimens for the treatment of both mild and severe hay fever. Dimethothiazine (Banistyl), also shown to be useful, has since been withdrawn from prescription.