High-precision mass measurement equipment is required in some areas of science and technology. Physics, chemistry, pharmaceutics and high precision mechanics are common examples. In metrology, high-precision scales are used for verification and calibration of lower precision mass measurement equipment (weights and scales). Mass comparators are the most accurate mass measurement instruments available today. It is a special type of electronic scales designed to compare mass of two weights. They can be automatic or manual, with various measurement ranges and accuracy classes. This article discusses principles of operation of mass comparators and practice of high-precision mass measurement. There are special computer programs that can be used in conjunction with these instruments, which may significantly improve measurement accuracy (when mass comparator is controlled remotely) as well as simplify calculations and reporting procedures. This article describes one of these programs – ScalesNet32 – which can be used with mass comparators produced by Sartorius (Germany).