The present paper presents a stochastic seismic analysis of fluid and fluid-solid systems by using Lagrangian approach. For this reason, authors have programmed variable-number-nodes two-dimensional isoparametric fluid finite elements in FORTRAN and have incorporated into a general-purpose computer program for stochastic dynamic analysis of structure Systems, STOCAL. For numerical examples, a rigid fluid tank and a fluid-solid interaction system are selected. Natural frequencies from the modal analyses of the fluid and fluid-solid systems are compared with those of analytical and numerical solutions. S16E component of the Pacoima Dam record of the San Fernando Earthquake in 1971 is used as a ground motion. The mean of maximum values from stochastic analysis are compared with deterministic analysis results.