Mouthings and mouth gestures are omnipresent in Sign Language of the Netherlands (NGT). Mouthings in NGT commonly have their origin in spoken Dutch. We conducted a corpus study to explore how frequent mouthings in fact are in NGT, whether there is variation within and between signs in mouthings, and how frequent temporal reduction occurs in mouthings. Answers to these questions can help us classify mouthings as being specified in the sign lexicon or as being instances of code-blending. We investigated a sample of 20 frequently occurring signs. We found that each sign in the sample co-occurs frequently with a mouthing, usually that of a specific Dutch lexical item. On the other hand, signs show variation in the way they co-occur with mouthings and mouth gestures. By using a relatively large amount of natural data, we succeeded in gaining more insight into the way mouth actions are utilized in sign languages.