This project utilises innovative methodology to evaluate the suitability of novel three-dimensional (3D) cell culture models for investigating anti-cancer drug activity. 3D cell culture methodology was utilised as this in vitro approach is considered to recapitulate the in vivo conditions more accurately than two-dimensional (2D) monolayer cell culture. Two separate 3D cell culture model formats were developed which are amenable to automated liquid handling systems, and a variety of instruments for total well fluorescence and confocal imaging. The first 3D cell culture assay developed was in a 384-well format, and was validated as suitable for use for drug discovery. The second 3D cell culture assay was optimised for 1536-well format, specifically created for extensive drug combination studies. The 3D breast cancer cell culture assay developed for drug discovery utilised the breast cancer cell lines of MDA-MB-231 (endocrine receptor- and ErbB2 receptor-negative), MCF-7 (endocrine receptor-positive) and BT-474 (ErBb2 receptor over-expression). This 3D cell culture assay was miniaturised to a 384-well format, developed to be semi-automated and was thoroughly characterised for sensitivity and reproducibility. In addition, measurements of metabolic activity or spheroid morphology can be utilised for determination of drug activity. To validate the 3D breast cancer cell culture assay for use in high-throughput applications, a pilot screen comprising of 741 clinically relevant drugs was completed. Results from the pilot screen identified a number of drugs with anti-breast cancer activity that warranted further investigation. The drugs of interest were a mixture of drugs with both novel and demonstrated anti-cancer activity.