A testing apparatus has been developed to measure the hydraulic conductivities both normal to and in the plane of a geotextile specimen. For the in-plane flow condition, the system is also capable of measuring the hydraulic conductivity of the geotextile in the confinement of a soil under a specified confining pressure. This paper briefly describes the apparatus, the testing program and the in-plane hydraulic behavior of a nonwoven geotextile and a woven-nonwoven composite geotextile. The test results show the requirement of in-soil testing for actual simulation of the field condition.