  In this article we study the mean return times to a given set for suspension
flows. In the discrete time setting, this corresponds to the classical version
of Kac's lemma \cite{K} that the mean of the first return time to a set with
respect to the normalized probability measure is one. In the case of suspension
flows we provide formulas to compute the mean return time. In particular, this
varies linearly with continuous reparametrizatons of the flow and takes into
account the mean escaping time from the original set.
