Combining forms (CFs) are bound lexical elements which are abundant in the English language, such as the well-established CFs eco-, geo-, -holic, and -athon. In the 20th century, a new class of so-called ‘native combining forms’ emerged. These often occur in jocular formations, predominantly on the Internet. They are used to name new cultural phenomena and have given rise to a considerable number of neologisms in the past two decades. This chapter presents the results of a corpus study of the productivity of native CFs in written American English. The productivity of 21 CFs was examined diachronically from 1950 until 2009 using the Corpus of Historical American English (COHA). The aim of the study was to determine whether the elements investigated are currently productive and how this productivity has changed over time. A further aim was to identify factors influencing productivity and to establish a connection between an element’s productivity and its topicality.