Specific immunotherapy is effective in alleviating symptoms in grass pollen-induced rhinitis, but there are no clear data demonstrating a correlation between symptom-medication scores and objective parameters. Twenty-five patients taking part in a double-blind, placebo-controlled immunotherapy with mixed grass pollen-formalinized allergoids were studied. All patients had the same investigations. Symptom-medication scores were significantly (p less than 0.005, Mann-Whitney U test) reduced in the treated group by comparison to the placebo-treated patients. Nasal challenges performed with threefold increasing numbers of orchard grass-pollen grains demonstrated that patients treated with allergoid tolerated a significantly (p less than 0.005, Wilcoxon W test) greater number of grains after treatment, whereas there was no mean difference in the placebo-treated patients. There was a significant (p less than 0.005, Spearman rank-correlation) correlation between nasal challenges and symptom scores during the season. The skin prick test end point was significantly (p less than 0.001, Wilcoxon W test) reduced after treatment in the allergoid-treated group and remained unchanged in the placebo-treated group. There was a significant (p less than 0.001) correlation between the skin prick test end point and symptom scores during the season. Serum grass-pollen IgG titrated by a solid-phase radioimmunoassay with Staphylococcus A protein was significantly (p less than 0.01, Wilcoxon W test) increased after treatment with allergoid, but there was no significant correlation between IgG titer and symptom scores during the season. Serum grass-pollen IgE increased (p less than 0.04, Wilcoxon W test) in the treated group but there was no correlation with symptom scores.