LabData consists of a graphical user interface front-end in MS Access, which is connected to tables, procedures, triggers and queries running on an SQL server back-end. LabData allows the interpretation of multi-tracer datasets and hydrochemistry in groundwater, using interpretational models such as mixing or lumped parameter models (convolution integrals) to determine the mean residence time. Data import from and to Excel is supported in a flexible and user-friendly way. Any measured parameter can be plotted against any other and compared to modelled curves in the Excel output. First impressions on the spatial data distribution are possible exporting data as coloured dot maps to Google Earth. Its main application is Isotope Hydrology and Environmental Tracers, for which it has special post-processing features. These include the electrolytic enrichment of tritium and radiometry with Liquid Scintillation Counting (LSC) and gas proportional counters, gas chromatography, and Noble Gas Mass Spectrometry. LabData comes with three documentation files which allow to get the system up and running (the LabData Tutorial), documents the Lumped Parameter Modelling capabilities (Lumpy Manual) and a more detailed (but incomplete and steadily in development) LabData Manual on the system as a whole. The back-end database structure on MS SQL Server is created executing the SQL files. LabData sits under a GNU-GPL licence.