The Spatial Data Transfer Standard (SDTS) was approved as Federal Information Processing Standard (FIPS) 173, effective February 1993. Federal agencies and geographic information system vendors currently are developing SDTS encoding and decoding capabilities. A program is being developed to test encoders and decoders for conformance to the requirements of SDTS profiles. A series of test points will specify SDTS requirements that can be tested by software or by nonautomated methods. By certifying SDTS products, the conformance testing program will benefit both vendors and users of the SDTS.