BACKGROUND: Use of the QuantiFERON®-TB Gold In-Tube assay (QFT-GIT) in remote areas is limited by the need to incubate blood samples within 12 h of collection. PortaTherm™ is a portable, electricity-free, phase-change incubator previously used for field collection of microbiological samples. OBJECTIVE: To determine whether the PortaTherm can be used for the reliable incubation of QFT-GIT samples, thus enabling QFT-GIT use in settings distant from laboratory facilities. METHODS: In a prospective comparative study in Peru, blood samples were collected from 50 participants and processed in three parallel QFT-GIT tests per participant; two were incubated in a conventional incubator; the third was incubated in the PortaTherm. RESULTS: All 150 QFT-GIT tests gave definitive results, and for 46 of the 50 participants all three tests were concordant, eight of which were positive. Four participants had one discordant result: two due to discordance of a conventional incubator QFT-GIT result, and two due to discordant PortaTherm QFT-GIT results. CONCLUSION: The QFT-GIT inter-incubator variability between the PortaTherm and conventional incubator was no greater than the intra-incubator variability for the conventional incubator, indicating that the Porta-Therm is a suitable tool for incubating QFT-GIT whole blood samples in remote settings where access to a laboratory or electricity is limited. © 2010 The Union.