The modern clinical chemistry laboratory is characterized by a high degree of the labor process automation, which, with an undeveloped methodology for estimating labor costs, creates the problem of staff work rationing. This prevents the objective formation of staffing and load accounting, and also does not allow predicting an effect of changes in order to optimize work processes. The aim of the study was to assess the structure and the magnitude of labor costs components at a serum assay automated workplace and to characterize its impact on the staff workload and the testing labor intensity. The time-and-motion study of staff labor costs when working on the Roche Cobas 6000 (Roche Diagnostics, Switzerland) modular platform was carried out at the «Eurotest» laboratory, Moscow. We applied the author's research methodology to obtain and analyze the data. As a result, we determined a classified list of the standard manipulations that form the workplace labor process, and measured their duration. The data obtained was presented in the form of stratified components, as fixed or variable labor costs (as the labor time). Based on that, we carried out modeling of changes in the workplace total labor costs and the labor intensity per test for different work scenarios, depending on the volume of tests and the number of tests performed from a serum specimen. It has been established that the most significant part of the variable labor costs (up to 28 seconds per laboratory test) is created by manually transferring laboratory information, and a fully functioning laboratory information system can increase the labor productivity by at least 2.6 times. Another key factor in reducing the costs is an increase in the number of tests performed from one specimen. We can conclude that despite the automation, the variable labor costs dominate the serum assay workplace and it requires flexible methods of the labor rationing. The proposed method allows both to calculate the labor intensity of laboratory tests with an arbitrary volume, a statistical ratio of different tests, a configuration of tests performed from one specimen, and to predict an effect of measures aimed at optimizing the work of the laboratory. © 2023, Klinichescheskaya Laboratornaya Diagnostika. All rights reserved.