Purpose: The aim of this literature review was to investigate the results from in vitro laboratory studies on the influence of temperature and relative humidity present before polymerization on enamel and dentin bonding systems. Materials and Methods: A systematic search was carried out including articles published in English, in peerreviewed journals, and indexed in MEDLINE/PubMed database. The search was carried out using the terms: relative AND humidity AND dental. In vitro studies were retrieved and divided into laboratory simulation studies and studies on physical properties. Laboratory simulation studies were addressed by subtopic: resin-enamel bond strength, resin-dentin bond strength, and dentin-enamel microleakage. Studies on physical properties tested the influence of humidity and temperature through polymerization contraction, flexural strength, and dentin wettability. Results: Laboratory simulation studies demonstrated a strong influence of humidity and temperature on dentin and enamel bond strength and microleakage with dental adhesives systems. The studies on physical properties failed to demonstrate any influence of humidity on the adhesion performance, except for wettability measurement. Conclusion: The clinical relevance of these in vitro results remains to be demonstrated. A review of in vivo clinical studies will complete the literature data presented here. Keywords: relative humidity, temperature, enamel bonding, dentin bonding, polymerization, review