Abstract: Many of the real life problems are modelled as second order timeinvariant
singular linear systems Ex¨ = A1x˙ + A2x + Bu, y = Cx that we represent by quintuples of matrices (E;A1;A2;B;C). Controllability and observability are qualitative properties largely studied by different authors however, no scheme for computation of control and observer was proposed. In this paper we study the controllability and observability character of second order singular linear systems by means the ranks of certain matrices depending only on the matrices E, A1, A2, B and C.