Triacsin C was previously reported to inhibit long-chain acyl-CoA synthetase and to reduce the production of acyl-CoA in rat neutrophils dose- and time-dependently. We found that preincubation with triacsin C inhibited the incorporation of labeled arachidonic acid into rat neutrophils. Furthermore, when triacsin C-treated neutrophils were stimulated with the Ca-ionophore A23187, they released an increased amount of eicosanoids into the culture medium. These results indicate that triacsin C suppressed acylation of arachidonic acid, which resulted in an increase in its metabolites.