Teratological variation in the segmental structure of the abdomen has been studied in five pseudoscorpion species of the European Neobisiidae, four from the genus Neobisium CHAMBERLIN and one species of the genus Roncus L. KOCH.A total of 78 abnormal specimens have been found. These were dissected thoroughly and subjected to the pathomorphological analysis. It was found that the frequency of anomalous pseudoscorpions was variable, depending on the collection site, developmental stage and species. The following aberrations of sclerite segmentation have been noted: partial atrophy, hemimery, symphysomery, occurrence of a supernumerary sclerite (?), and different combinations of these anomalies.Teratological variation of the abdominal sclerites has been confined mostly to adults, with the exception of a single tritonymph. Tergal anomalies have been much more frequent than those affecting sternites. It was also noted that segmental deficiencies occur more frequently in males than in females.In addition, some generalizations on the relative distribution of segmental anomalies have been made. The possible causes of the origin of these deficiencies in the pseudoscorpions studied have been also briefly discussed.