Monocyte activation with cytokine production is a well known event in the course of dialysis treatment but its relation to symptoms of haemodialysis or long-term pathological changes in chronic dialysis patients is still under discussion. Cytokine production depends on the balance between inducers and inhibitors while effects rely on the peculiar uraemic environment and cell metabolism. 'Foot-prints' for monocyte activation have been found, but no marker for clinical symptoms has been demonstrated clearly. In this scenario it is almost impossible to link a specific symptom to a definite stimulus such as dialysate microbial contamination or membrane complement generation. The topics discussed in this paper include cytokines synthesis modulation factors, levels in haemodialysis patients, and results of finding markers of clinical relevance. Special attention is paid to microbial contamination of dialysis fluid with analysis of cytokine inducing substances in commercial sterile solutions. Data on cytokine synthesis and activity in the aged are also discussed, with special regard to the haemodialysis setting.