This project will estimate the costs of illicit drug use in Tasmania in 2015-16, the effects of decriminalisation and what that cost would be if the use of illicit drugs was decriminalised. In the following section 1.1, it briefly outlines what are considered illicit drug in Australia and Tasmania. In section 1.2, illicit drug use in Australia compared to the rest of the world is examined. Sections 1.3 and 1.4 examine recent illicit drug use in Australia and Tasmania. Chapter 2 provides the data sources and explains the methodology and assumptions used to construct the estimate of the cost of illicit drug use in Tasmania in 2015-16. In particular, in section 2.1 it outlines the approach of neoclassical economics to cost-benefit analysis and the approach used in this limited study. Section 2.2 discusses methods used in the past and in this study to vale the loss of life. In section 2.4 the data sources for each of the four cost categories considered in this study: Crime, Death and Disease, Health and Road Accidents are given. The effects of decriminalisation upon the incidence of the various cost components are discussed in section 2.5 and the assumptions made listed. The estimates of the cost of illicit drug use in Tasmania under the current law in 2015-16 and under decriminalisation are presented in chapter 3. The costs under the current law and decriminalisation are presented for each cost component Crime in section 3.1, Death and Disease in section 3.2, Health in section 3.3, Road Accidents in section 3.4 and summarised in Section 3.5. Section 4 concludes the report.