The paper formulates the problem of optimal linear control in tho presence of controlled input derivatives, unambiguously, for the first time. A correct solution to tho problem is provided for the case of system step disturbances. It is also shown that previous attempts to formulate this problem have been imprecise and this has led to the introduction of unnecessary assumptions and the use, in one instance, of an illogical performance index. Previous attempts to solve the problem have been shown to produce only incorrect results.