Note 4 at Ac 19:29: This cannot be the same Gaius as mentioned in Ac 20:4, because special mention is made of this Gaius being of Macedonia (see note 1 at Ac 16:9), whereas the Gaius of Ac 20:4 was from Derbe (see note 5 at Ac 14:6) in Asia (see note 3 at Ac 16:6).

There is also a Gaius spoken of in Ro 16:23 as being Paul's host while he was in Corinth and whom Paul spoke of in 1Co 1:14 as being one of the few people he baptized in Corinth.

The Apostle John addressed his third epistle to Gaius. We don't know which of these three Gaiuses was being referred to, or if this was yet another man of that name.

The only definite information we have on the Gaius mentioned here is what this verse says about him. He and Aristarchus (see note 5 at this verse) were Paul's traveling companions who, in his absence, suffered persecution in the theater in Ephesus.

Note 5 at Ac 19:29: This is the first of five times that Aristarchus is mentioned in Scripture (Ac 19:29, 20:4, 27:2; Col 4:10; and Phm 24). Aristarchus was from Thessalonica (Ac 20:4 and 27:2, see note 3 at Ac 17:1), and along with Gaius (see note 4 at this verse), he was persecuted in the theater in Ephesus. Aristarchus survived the persecution at Ephesus, as can be seen by the fact that he accompanied Paul on his return trip to Asia (see note 3 at Ac 16:6) a few months later (Ac 20:4) and was also Paul's companion during his voyage to Rome (Ac 27:2).

When Paul wrote to the Colossians from Rome, he spoke of Aristarchus as being his fellow prisoner (Col 4:10). Paul also wrote a letter from Rome to Philemon, who is supposed to be a believer of Colosse (Phm 2 and Col 4:17), that mentioned Aristarchus as a fellow laborer (Phm 24).