The purpose of this study was to determine the association between the 24-hour full moon phase of the lunar cycle and the admission of adolescents to in-patient psychiatric facilities in Oklahoma City, Oklahoma. Archival data from two major psychiatric facilities in the Oklahoma City area were gathered and utilized for this purpose. The data covered a three and one-half year period. The total number of patients assessed during that period was 17,930 and resulted in an admission rate of 10% for adolescents. The theoretical concept for this study was based on environmental, developmental, and behavioral psychology. Prior studies have had conflicting results in both their results and defining the variable full moon phase. Definitions have varied from a 24-hour phase to as long as 168-hour phase. The target populations of previous studies have been adults or groups of participants covering adolescents and adults without separation. To extend the prior research this study looked at a population of adolescents (ages 12 thru 19). The data were examined using a chi-square analysis with a result of X² = .086. These results fail to reject the null hypothesis and do not provide support for the alternative hypothesis. Thus, a greater number of admissions per day of adolescents to psychiatric facilities was not associated with 24-hr full moon phase days relative to non-24-hr full moon phase days.