The impact of cell (mobile) phone use on driving performance has been widely questioned for 20 years. This paper reviews the literature to evaluate the extent to which phoning may impact behaviour with a risk to affect safety. After analysing epidemiological studies that give an overview of cell phone use, this paper examines the experimental results and focuses on variables showing that driving is impacted by holding a mobile-phone conversation. Information processing (e.g. reaction time and detection rate of cues related to driving information) and variables associated with vehicle control (e.g. lane-keeping, headway and vehicle speed) seem the most relevant. Although less studied than behavioural indices, physiological data give information about the supplementary potential strain that the driver may undergo under dual-task conditions. This first part of the review highlights common findings, questionable results and differences among studies, which originate from specific experimental designs with particular dependent variables, i.e. self-report, behavioural and physiological indicators. Finally, how drivers try to compensate for the additional load brought by phone use is described. STATEMENT OF RELEVANCE: The two papers review the influence of mobile-phone use on driving performance. While there is ample evidence that this dual task is likely to increase the risk of car crash, the review analyses the variables eliciting detrimental conditions and, conversely, those that may preserve acceptable conditions for safety, close to usual driving. The decision of answering or initiating a cell phone call while driving depends upon the complex interaction among several variables, including driving conditions and driver's own characteristics. In addition, this decision remains under driver's awareness of being able or not to manage the two tasks simultaneously.