This volume is a special issue of Exceptionality, and explores meta-analysis research in special education. The contributors, who include S.R. Forness, M.P. Mostert, T.E. Scruggs and M.A. Mastropieri, discuss topics such as: special education and related services - what we have learned from meta-analysis; the characteristics of meta-analysis reported in mental retardation, learning disabilities and emotional and behavioural disorders; summarizing single-subject research - ideas and applications; and decision-making in special education - the function of meta-analysis.