This was a pilot study to investigate the new technique of laser Doppler imaging (scanning laser Doppler) as a tool to quantify microvascular blood flow in the digits of patients with primary Raynaud's phenomenon (PRP) and systemic sclerosis (SSc), and to determine in the first instance whether the flux patterns obtained differ between patients with SSc, patients with PRP, and healthy control subjects. Laser Doppler images of the dorsum of the hand and fingers were acquired at 23 and 30 degrees C in 17 healthy control subjects, 7 patients with PRP, 9 patients with the diffuse cutaneous variant of SSc, and 24 patients with the limited cutaneous variant of SSc. Different flux parameters were compared between groups. Analysis of variance found significant differences between groups in two tests: maximum difference in flux between fingertips of the same hand at 23 degrees C (P = 0.001) and maximum gradient in flux along a finger ("distal-dorsal" flux difference) at 30 degrees C (P = 0. 019). Post hoc tests highlighted the differences between controls and patients with limited cutaneous SSc. This pilot study suggests that laser Doppler imaging may allow objective measurement of microvascular flow in patients with PRP and SSc. This new technique may overcome many of the problems inherent in single-channel laser Doppler equipment. Copyright 1999 Academic Press.