Abstract: A method of assessing toxicity of a candidate agent to a sample of cells comprises the steps of providing a sample of cells, exposing the cells to the candidate agent for a suitable period of time, assaying the cells to measure data for at least one parameter of cellular function; and correlating the measured data of the at least one parameter of cellular function with toxicity, wherein the step of exposing the cells to the candidate agent is carried out in the presence of a reagent capable of facilitating transport of the candidate agent into the cell. The transport reagent may be an endocytosis, pinocytosis inducing agent, a peptide, or a liposome. The at least one parameter of cellular function may be selected from the group consisting of: cell viability; proliferation rate; membrane integrity; and a metabolic parameter.