1. The structure of the Pirenaica, Verata, Guadarrama, Zamorana, Berciana, Granadina, Blanca Andaluza, Blanca Celtibérica, Murciana, Negra Serrana, Malagueña, Canaria, Palmera and Retinta goat breeds have been analysed. 2. Fourteen blood genetic systems were analysed: reduced glutathione (GSH), red cell potassium (Ke), haemoglobin (Hb), diaphorase (Dia), catalase (Ct), malate dehydrogenase (MDH), carbonic anhydrase (CA), X-protein (X), nucleoside phosphorylase (NP), alkaline phosphatase (Alp), amylase (Am), ceruloplasmin (Cp), transferrin (Tf) and albumin (Al). 3. Of the fourteen genetic systems studied, six were monomorphic (GSH, Ct, MDH, CA, NP and Cp) and eight polymorphic (Ke, Hb, Dia, X, Alp, Am, Tf and Al). Phenotypic and gene frequencies of the eight polymorphic genetic markers are reported.