This Data Supplement to the Lawrence Livermore National Laboratory's (LLNL's) annual Environmental Report 1999 was prepared for the U.S. Department of Energy. The main volume is intended to provide all information on LLNL's environmental impact and compliance activities that is of interest to most readers. The Data Supplement supports main volume summary data and is essentially a detailed data report that provides individual data points, where applicable. Some summary data are also included in the Data Supplement, and more detailed accounts are given of sample collection and analytical methods. The two volumes are organized in a parallel fashion to aid the reader in crossreferencing between them. This supplement includes more detailed information to support the nine chapters in the main volume that cover monitoring of air, air effluent, sewerable water, surface water, ground water, soil and sediment, vegetation and foodstuff, environmental radiation, and quality assurance. The other five chapters in the main volume have no supporting information in the Data Supplement.