In 1997, he began a long association with DC Comics, beginning with a nearly 60-issue run on the Peter David written Supergirl series.

He penciled the Fred Van Lente written Scorpion story in the Marvel anthology title Amazing Fantasy.

Later in 2006, Kirk signed an exclusive deal with Marvel Comics,[1] his first project being a six issue Jeff Parker written Agents of Atlas miniseries, which included Wakandan-born S.H.I.E.L.D.

[2] In 2011 Kirk began a run on X-Factor, reuniting him with his Supergirl collaborator, Peter David, penciling issues 225 - 228.

David has named Kirk one of the three artists whose art has mostly closely matched the visuals he conceived when writing comic book scripts (the others being George Pérez and Dale Keown).