To determine whether nasal obstruction in children results in impaired nasal function, olfactory sensitivity was assessed in 65 children with various degrees of nasal obstruction and in 13 children without nasal obstruction. Overall, olfactory detection thresholds were directly related to clinical ratings of degree of nasal obstruction. Of the subjects with nasal obstruction attributable to adenoid hypertrophy, 28 received adenoidectomy; when retested 2 to 28 months later, 20 of the 28 subjects showed generally commensurate reductions in nasal obstruction ratings and olfactory detection thresholds. In a comparison subgroup of 16 subjects retested after intervals of 5 to 13 months without having received intervening adenoidectomy, both the nasal obstruction ratings and the olfactory detection thresholds remained relatively unchanged. These results suggest that, in children, nasal obstruction of varied degree is associated with commensurate impairment of the ability to smell, and that reduction in the degree of nasal obstruction results in commensurate recovery of the ability to smell. Olfactory function, although hitherto accorded little pediatric attention, deserves consideration both in weighing the importance of nasal obstruction in children and in deciding about therapeutic intervention.