Two unusual complications are described in a patient who had chronic lymphatic leukaemia. Spontaneous rupture of the spleen occurred and was related to subcapsular infarction and haemorrhage. The possibility of this complication should always be considered when signs of an acute abdomen develop in a patient with leukaemia. The phenomenon of pseudo-hyperkalaemia was demonstrated. This was most likely due to increased leucocyte fragility in vitro.