This study provides analyses and profiles of illegal drug usage in the Republic of Ireland. Two questions are addressed: a) can individuals be grouped into homogeneous classes based upon their type of drug consumption, and b) how do these classes differ in terms of other key background variables? The data reported in this study is from the National Drug Treatment Reporting System database in the Republic of Ireland. All analyses were carried out in collaboration with the Drug Misuse Research Division (the Irish REITOX / EMCDDA focal point). This database contains information on all 6994 individuals who received treatment for drug problems in the Republic of Ireland during 2000. The analysis was conducted in four steps. First, a single class model was examined in order to establish the respective probability associated with each drug type. Second, a series of unconditional latent class models was examined. This was done to establish the optimal number of latent classes required to describe the data, and to establish the relative size of each latent class. From this analysis the conditional probabilities for each individual, within a given class, were examined for typical profiles. Third, a series of conditional models was then examined in terms of key predictors (age and early school leavers). This analysis was conducted using MPlus 2.13. In the final stage of the research, the parameter estimates obtained from the multinomial logistic regression model (that was previously used to express the probability of an individual being in a given latent class, conditional on a series of covariates) were graphically modelled within EXCEL and the respective functions described. The results from this analysis will be described in terms of a) the profiling of typical serious drug misuse in Ireland, b) the clustering of drug types and, c) the respective importance of key background variables. The various profiles obtained are discussed in terms of health care strategies in Ireland.