Electronic Journal of Differential Equations, Vol. 2010(2010), No. 18, pp. 1-9. Title: Transport operator on phase spaces with finite time of sojourn property Author: Mohamed Boulanouar (LMCM-RMI, Poitiers, France) Abstract: In this article, the transport operator with general boundary conditions is discussed. According to a smallness hypothesis on the boundary operator and to finite time of sojourn property of phase spaces, we prove that the transport operator generates a strongly continuous semigroup and we give its upper bound. Submitted November 29, 2009. Published January 27, 2010. Math Subject Classifications: 47D06, 82D75. Key Words: Positivity; strongly continuous semigroups; transport operator.