The role of polymorphonuclear cells (PMNs) in the pathophysiology of ischaemic vascular disease has been increasingly recognized in recent years. Activated PMNs may physically obstruct blood flow. Subsequent release of reactive oxygen radicals and lytic enzymes lead to continued damage. Previous studies have shown increased white cell activity in patients with secondary Raynaud's syndrome (RS). However, whether this is related to the underlying condition or to digital vasospasm is not clear. Using a more physiological whole blood PMN aggregation assay, we assessed PMN activity in 38 patients with severe Raynaud's phenomenon (RP) [16 had systemic sclerosis (SSc) and secondary RS; 22 had RP alone and no other features of a connective tissue disease]. Additionally, plasma levels of malondialdehyde (MDA), an indicator of free radical activity, were measured. Results were compared with those obtained from 56 matched volunteers. In order to assess if changes in PMN activity was directly related to digital vasospasm, patients were asked to record the duration and frequency of their Raynaud's attacks during a 2-week period using a pocket sized diary. Correlation between these clinical variables of Raynaud's severity and white cell activity was assessed. Patients with RP, both with and without SSc, showed a significantly greater fall in single PMN count when compared with control subjects [SSc associated RS 48.2 (41.4-56)% versus control, P = 0.04; RP alone 49.3 (46.8-52.1)% versus control, P = 0.01 (Mann-Whitney U-test)].(ABSTRACT TRUNCATED AT 250 WORDS)