We report studies on the efficiency of mid-infrared laser ablation of bovine cortical bone using a free-electron laser when the ablation zone is irrigated with chemically inert and biocompatible perfluorocarbon compounds. Bovine bone samples were cut into slices with thicknesses ranging from 0.2mm to 4.0 mm. At wavelengths of 2.94, 6.1 and 6.45 micrometers the water and collagen in the bone matrix absorb the laser radiation; the perfluorocarbons transmit light at all these wavelengths, albeit with drastically varying absorption coefficients. The perfluorocarbons also dissipate heat and acoustical stress, and, under optimal conditions, prevent carbonization of the bone. The ablation efficiency - as well as plasma and bubble formation, acoustic signals and carbonization - are critically dependent on the molecular weight of the perfluorocarbon compound and its thickness. The ablation efficiency was determined as a function of wavelength, scanning speed, number of scans, and perfluorocarbon species and thickness. The laser fluence was estimated to be in the range 35 J/cm2-70j/cm2 for all wavelengths; the scanning speed was varied over the range 40micrometers /s-2960 micrometers /s. The ablation rate was estimated from scanning electron microscopy to be 0.5 mm/s. This is higher than that reported for ns Er:YAG and Q- switched CO2 lasers. The morphology of the ablation cuts at 2.94micrometers suggests a possible role for nonlinear absorption in the bone.