The non-native vascular flora of Massachusetts is listed with earliest and latest dates of occurrence. Each entry is annotated to indicate which taxa have become established members of the flora and which have not. Specimen data were compiled from over 25 herbaria, supplemented by reports from early floristic publications. A total of 1317 non-native taxa are documented; 737 are treated as established members of the state's flora (29% of the flora); 23 taxa persist at or near former human habitations (1%); 559 taxa are treated as non-established waifs (22%). The current figure of 30% alien taxa is similar to other New England states and is a significant reduction from the 45% tallied in the 1999 state flora. A revised statistical summary of the state's vascular flora is provided.