Kavanagh was a Marvel Comics editor during the late 1980s and 1990s. Titles he edited during that time included Marvel Comics Presents and Nick Fury, Agent of Shield.

During the mid and late 1990s he began to write for Marvel, on titles such as Moon Knight, Avengers Timeslide, X-Man and X-Universe. During his run on Web of Spider-Man he pitched a storyline involving the return of the clone, which then formed the basis of the Clone Saga.

In the X-Men '99 Annual his name is misspelled in binary on the first page. "TERRY RULES" can be found in binary on the second and third pages.

Comics work includes:

• Fantastic Four 2099 #6-8