This thesis tests the hypothesis by Kandel (1975) that there is a specific sequence of drug use that users follow. Using the same scalogram analysis technique utilized by Kandel in her original Gateway Hypothesis study, a distinct sequence of use was discovered. This thesis is based on the National Survey on Drug Use and Health (2005). This study confirmed Kandel's earlier findings in that this study determined that there is a sequence of drug use. The current study also confirms Kandel's position that licit drugs precede the use of illicit drugs. This study's findings differ from those of Kandel, however, in that tobacco and not alcohol was found to be the first drug of experimentation. In the current study, the data were divided into two age cohorts to determine if changing the legal drinking age had any impact on sequencing. Findings indicate that the change in the legal drinking age had no effect on sequences of drug use. Binomial logistic regression analysis results support the scalogram analysis findings, resulting in the rejection of the null hypotheses that there is no sequence to drug use, that the sequence is tobacco, alcohol, marijuana, hard drugs, and that the change in the legal drinking age would affect sequencing for those respondents who could not drink legally until the age of 21.