Dictyocaulus viviparus, the lungworm of cattle, is not commonly diagnosed as a clinical entity in cattle native to Iowa. The parasite is sporadically distributed throughout North America, however, and cases do occasionally occur in the upper Midwest with serious clinical consequences and apparent overwintering of the larval forms. Lungworm infection should be considered as a diagnostic possibility in cases of chronic respiratory disease that do not respond to therapy for other types of infection. The disease can be diagnosed by identifying larval forms in feces by the Baermann technique or by finding adults in the respiratory system at necropsy. A field case from an Iowa dairy herd is described.