This paper gives the necessary and sufficient condition for the reachability of the sampled-data system S-1 obtained by tile discretization of a linear time-invariant continuous-time system with a first-order hold. Equivalence of the reachability and controllability of S-1 is also shown. Similar results are given also for observability and reconstructibility. It turns out that S-1 is reachable only if S-0 is reachable, while S-1 is observable if and only if S(4)l0 is observable, where S-0 is the sampled-data system obtained by the discretization with a zero-order hold of the same sampling period.