Later that year, on stardate 3045, the Enterprise visited Cestus III in response to a faked invitation from Commodore Travers. The message, actually a Gorn ruse, asked that Kirk bring his senior tactical officers down for a conference and dinner. The landing party was ambushed; Kelowitz was the only surviving tactical officer. (TOS: "Arena")
Kelowitz was part of the landing party to Omicron Ceti III on stardate 3417, and he was paired with Lieutenant Hikaru Sulu in investigating the mysterious colony there. It was Kelowitz who first noticed there were no animals on the planet. Later, he was taken over by alien spores, though the spores were eventually destroyed by a subsonic transmitter. (TOS: "This Side of Paradise")
Kelowitz was played by Grant Woods.
The final draft script of "Arena" reveals that this character's role in that episode was at one point intended to have been filled by a new character named Molton, who the script describes as a "tactics officer".
Many reference works refer to Kelowitz as a lieutenant commander, although he wore the braid of a full lieutenant in every appearance he made. He apparently was confused with Lang, who – despite wearing lieutenant commander stripes – was consistently called "Lieutenant Lang" in references. An actual inconsistency exists, however, in that Kelowitz wore a blue sciences division uniform despite being referred to as a tactical officer in "Arena". It seems likely he could be a "generalist" officer who served between a few departments, as Kevin Riley, Kyle, and Leslie had been known to do, or simply that he served in a science department which performed a tactical function.