Abstract: 1. Metal complex formazan dyestuffs which in the acid form are represented by the formula: ##STR1## wherein A and B are each selected from phenylene, naphthalene, substituted phenylene or substituted naphthalene groups, said substituted phenylene or substituted naphthalene groups containing at least one group selected from SO.sub.3 H, PO.sub.3 H.sub.2, CO.sub.2 H, CN, NO.sub.2, NH.sub.2, acetylamino, benzoylamino, OH, F, Cl, Br, C.sub.1-4 alkyl, C.sub.1-4 alkoxy, sulphonamido, ##STR2## wherein Y = CO or SO.sub.2 and n=0 or 1 or H.sub.2 O.sub.3 P--CH.sub.2 CH.sub.2 --NH--Y-- wherein Y = CO or SO.sub.2 ;D is NO.sub.2, CN, COOH, SO.sub.3 H, C.sub.1-4 alkyl, C.sub.1-4 alkyl substituted by PO.sub.3 H.sub.2 ; C.sub.1-4 alkenyl, styryl, pyridyl, furyl, COCH.sub.3, CO.sub.6 H.sub.5, naphthyl, phenyl or phenyl substituted by at least one group selected from COOH, NH.sub.2, CN, F, Cl, Br, acetylamino, benzoylamino, OH, methyl, methoxy, SO.sub.3 H and PO.sub.3 H.sub.2 ;X.sup.1 and X.sup.