An evaluation is given of some morphotaxonomic criteria used for specific distinction in the genus Acrochaetium. 59 isolates from the European Atlantic coast were compared after having been cultured under uniform conditions. As a result, three species are distinguished, primarily on the characters cell length, arrangement and length of the monosporangia. Cell diameter and shape of the monosporangia and monosporangial stalk cell may sometimes be used as additional characters for identification purposes. Recognized taxa have not undergone formal nomenclatural revision, and their identification has been provisional; they are: A. zosterae Papenfuss, A. nemalionis (De Notaris) Bornet, and A. daviesii (Dillwyn) Nageli. Because of large intraspecific variation, differences between the three are not very clear cut. Sexual life histories are known from culture in the first two species. Comparison with relevant literature shows some of the commonly used criteria for species distinction to be of little value. The position of the genus Acrochaetium within the family Acrochaetiaceae is briefly discussed