A semantic contrast between verbs taking the -um- paradigm and those taking the mag- paradigm is known to exist in Tagalog and Waray-Waray but is virtually absent in all varieties of Bikol and most Bisayan languages. Evidence is presented from Fr. Marcos de Lisboa's seventeenth-century Vocabulario de la Lengua Bicol that many Old Bikol verbs had contrasting -um- and mag- conjugations. The -um- and mag- conjugations of Old Bikol are compared with those of Waray-Waray, Southern Tagalog, and Rinconada Bikol. After a discussion of the categories of semantic contrast between -um- and mag- verbs in Old Bikol, and how these contrasts were restructured in Modern Bikol, a progression of stages is proposed to explain how the -um- vs. mag- contrast has been lost in Bikol and other Central Philippine languages.