We investigated whether Al-gel could adsorb and release FSH effectively in vitro and in vivo, and whether a single administration of FSH in Al-gel could successfully induce superovulation (SOV) in cattle. Porcine FSH (pFSH; 30 mg) was mixed with 5 mL of Al-gel; 99.98+/-0.01% of pFSH was adsorbed by the gel and 71.6+/-1.1% of the adsorbed pFSH was subsequently released in the presence of BSA. In cattle given a single i.m. treatment of 30 mg of pFSH in 5 mL of Al-gel, the numbers of CL, total ova recovered, and transferable embryos per cow were not significantly different from conventional (twice daily for 4 d) pFSH treatment (12.3+/-1.7 versus 11.7+/-1.8, 10.0+/-2.5 versus 9.3+/-1.7, and 8.6+/-2.3 versus 8.0+/-1.8, respectively, mean+/-S.E.M.); plasma pFSH concentrations were increased for 4 d, indicating sustained release from the Al-gel. Five cows were given 30 mg pFSH in 5 mL of Al-gel i.m. on five occasions (once every 2-3 months); there was no significant difference among treatments for the number of CL (12.4+/-3.8, 13.8+/-4.8, 9.0+/-1.9, 9.8+/-3.0, 12.0+/-2.1), total ova recovered (12.0+/-3.8, 12.6+/-5.1, 6.8+/-1.9, 7.6+/-1.8, 11.4+/-2.5), and transferable embryos (11.4+/-3.9, 10.4+/-5.8, 6.6+/-2.1, 4.8+/-1.4, 10.4+/-2.6). In conclusion, a single i.m. treatment of 30 mg pFSH in 5 mL Al-gel effectively induced SOV in cattle.