The basal temperature of the hands has been measured by quantitative thermography in a group of normal controls and rheumatoid patients exhibiting Raynaud's phenomenon. The thermographic index for both the dorsum of the hand and the fingers was significantly lower in the patients with Raynaud's. Oral treatment with inositol nicotinate (Hexopal) was followed by an initial rise in the thermographic index in both areas. After the initial increase the temperature fell again but then rose after two months treatment. At nine months two subjects on continuous therapy had higher indices than the four who had discontinued therapy. It is suggested that long-term treatment with nicotinate acid derivatives may produce improvement in the peripheral circulation by a different mechanism than the transient effect detected by short-term studies.