A new protocol for titrating nonstabilized diazoalkane solutions by quantitative (19)F NMR is reported. An excess of 2-fluorobenzoic acid dissolved in CDCl(3) is treated with the diazoalkane solution at a low temperature, immediately forming the corresponding 2-fluorobenzoate ester upon warming. A significant difference in the (19)F chemical shift between the ester and acid is seen, allowing facile and accurate integration to determine titer. The procedure is safe, rapid, and indicates the active diazoalkane concentration with high precision.