AbstractVarious isolates of Cacao Swollen Shoot Virus (CSSV) were detected without difficulty in leaves of Theobroma cacao L. by ELISA and immunosorbent electron microscopy (ISEM) using an antiserum to severe strain 1A. Many isolates were detected with relatively high values at dilutions of 1:30, whereas some other isolates were hardly or not at all detected at this dilution. Strain 1A was detected at dilutions of up to 1: 2560 of crude leaf extracts. All isolates yielding high reactions seem to be serologically closely related to strain 1A. Strains of the mottle‐leaf type (AD 191, AD 196, AD 7, AD 36, AD 135, Kpeve) and others were poorly detected; their relationship to strain 1A is discussed. A close correlation was found between results obtained by ELISA and ISEM.