All exposure determinations and risk assessments ultimately depend on accurate chemical analyses, and therefore some critical aspects of analysis for 2,4-D residues have been included in the present document. The available analytical results concerning 2,4-dichioro-phenoxyacetic acid (2,4-0) and its derivatives in herbicides and biological and environmental matrices were collected over a span of almost 40 years, by diverse and, until fairly recently, not sufficiently specific or sensitive methods. This makes comparison of most of the data reported in the literature difficult.