Dietary treatment of rabbits with 1% cholesterol resulted in a transient rise in their plasma nitrate levels. After 3 weeks of treatment the nitrate levels were about 50% higher than those of the controls (p<0.005). After 10 weeks of treatment the nitrate levels were similar to those at the start of the study. In accordance with previous work (Xiu et al., J. Clin. Invest., 1994, 93, 2732-2737), the cholesterol treatment let to a decreased blood flow velocity in arterioli of the third order in the conjunctiva, and a decreased diameter of these arterioli. There was a significant correlation between plasma nitrate levels and the two microcirculatory variables (p<0.0001). Nitrate is the major metabolic end product of nitric oxide (NO), and plasma nitrate levels may be used as an index of the endogenous formation of NO. The present results suggest that dietary cholesterol induces a transient increase in the synthesis of NO. Such an increased synthesis may compensate for part of a cholesterol-induced degradation of NO.