We report the case of a 71-year old male patient with a chronic lymphoid leukaemia of 10 years' duration who abruptly suffered deterioration of this general condition and haematological disturbances suggesting worsening of this blood disease (Richter's syndrome). Blood cultures demonstrated a Campylobacter coli septicaemia. Treatment with antibiotics resulted in a return to the previous clinical and biological situation. The various visceral manifestation of the infection are discussed.