Human dental pulps obtained from normal teeth, hypersensitive teeth and teeth with inflamed pulp were studied to measure and to compare the endogenous levels of arachidonic acid metabolites in order to see the relative activities of the different pathways involved in arachidonic acid metabolism. Pulp homogenates were incubated with $^{14}C$-arachidonic acid and lipid solvent extracts were separated by thin layer chromatography (TLC) to be analyzed by autoradiography and TLC analyzer. 1. The most significant metabolite was HETEs showing $96.9{pm}37.8$pmol/mg tissue protein/hr in normal pulp, $169.2{pm}76.7$ in hypersensitive pulp and $385.4{pm}113.2$ in inflamed pulp. In normal pulp $LTB_4$, 6-keto-$PGF_{1alpha}+PGE_2$, $TXB_2$ and unidentified metabolite were formed in decreasing order. While in hypersensitive and inflamed pulp 6-keto-$PGF_{1alpha}+PGE_2$, $LTB_4$, $TXB_2$ and unidentified metabolite were formed in decreasing order. 2. In hypersensitive pulp only HETEs were significantly increased when compared with that in normal pulp. The levels of all the converted metabolites in inflamed pulp were significantly increased compared with those in normal pulp. In inflamed pulp, the levels of $TXB_2$ and HETEs were significantly increased compared with those in hypersensitive pulp. 3. The ratio of each metabolites to the total converted metabolites showed an increased value of $TXB_2$ and 6-keto-$PGF_{1alpha}+PGE_2$, as the degree of inflammation was increased, while that of HETEs decreased both in hypersensitive pulp and inflamed pulp more than in normal pulp. 4. The relative amounts of the total metabolites formed in lipoxygenase pathway to cyclo-oxygenase pathway were 6.8 fold in normal pulp, 4.4 fold in hypersensitive pulp and 3.8 fold in inflamed pulp.