The present study looks into the variations in the frequencies and pragmatic functions of the metadiscourse markers known as boosters, and in particular, with regard to their verb forms. Three corpora have been compiled to this end, covering the fields of engineering, medicine and linguistics. The corpora were manually annotated for metadiscourse markers, boosters included, by a group of annotators. A predetermined list was used for annotation, but throughout the annotation process the list was modified to better reflect the use of metadiscourse in the corpora. The raw count of the occurrences of verb boosters shows clear differences between the corpora, which in turn confirms previous studies of this type. However, the range of verbs identified was very similar, pointing to a large overlap among the three. The three top frequency verb boosters also showed a clear overlap for engineering and medicine, but revealed considerable differences with linguistics. This study has been conducted within a research project financed by the Spanish Ministry of Economy, Industry and Competitiveness (FFI2016-77941-P).