Findings show that mobile phone use is a regular part of many young adults' lives and is not restrained by the circumstances under which calls are received or made, whether in public or private. Those who engaged in high-level mobile phone use were more likely than low-level users to believe that they benefited psychologically, socially, and financially from their high-level use. Low-level users reported that the major factor that prevented them from high-level use was the cost involved. The availability of a mobile phone to receive and make calls in all types of circumstances is believed by some to reduce the quality and frequency of face-to-face conversations. In addition, private conversations are often conducted in public within hearing distance of friends and associates. Since mobile phone use is a relatively new behavior and norms for appropriate use are still developing, research should examine beliefs and attitudes about mobile phone use, followed by assessments of the benefits and adverse effects of various uses of mobile phones. Study participants were 197 introductory psychology university students (49 males and 148 females). Two waves of data collection were conducted 1 week apart. The wave-one questionnaire tested whether mobile phone use, particularly high-level use, was planned behavior that met particular daily needs of the user. The second wave of data collection assessed the level of mobile phone use during the previous week and mobile phone behavior in a variety of social situation. A pilot study was conducted to determine the belief-based measures used in the first questionnaire. 2 tables and 28 references