An outbreak of clinical dictyocauliasis in a dairy herd comprising twenty-six cows and five heifers is described. The index was a purchased animal which began coughing several days after introduction to the herd in March. A few weeks later several other cows started to cough, and by July the clinical signs became more severe; milk production decreased and affected animals lost weight. Clinical examination revealed moderate to severe bronchopneumonia. Fecal ecamination revealed Dictyocaulus viviparus larvae in eight animals resulting in a diagnosis of verminous pneumonia. Factors which could have favoured the development and survival of D. viviparus and were therefore assumed to contribute to the occurrence of the disease included pasture management, as the cattle grazed one of two pastures of only one and two hectares for 78 days from April to July, rainy weather and mild temperatures.