The effects of human monokines on calcium release from cultured newborn murine calvarium were studied. Highly purified interleukin 1 (IL-1) (17 kDa) and recombinant IL-1 beta in the concentration range 0.2-20 U/ml released significant amounts of calcium. Mean resorption indices (RI) at 0.2 U/ml were 1.28 and 1.49, and at 20 U/ml, were 1.82 and 1.72, respectively. Calcium release was abrogated by the cyclooxygenase inhibitor piroxicam. Thymocyte stimulating activity (TSA) 25-31 kDa alone at 0.14 U/ml released calcium in a prostaglandin dependent manner with a mean RI of 2.13, a significantly greater calcium release than that obtained by 17 kDa IL-1 at 20 U/ml. The 6-9 kDa inhibitor of IL-1 induced thymocyte proliferation alone also released calcium in a prostaglandin dependent manner with a mean RI of 2.29 at 200 inhibitory U/ml. Addition of 6-9 kDa IL-1 inhibitor to the 25-31 kDa material did not significantly change the calcium release, whereas addition of the inhibitor to 17 kDa IL-1 produced a significant increase in calcium release.