The kinetics of complexation of MnII, CoII and ZnII by isocitric acid have been studied by the stopped flow method at 15,25 and 35°C, ionic strength 0.20 M (NaClO4) and pH range 4.50–6.35. Under these experimental conditions, one process is observed for each system within a few seconds. A mechanism is proposed to account for the observed behaviour, which is associated with participation of the OH group in complex formation. Activation energies are also reported.