The paper presents the study on the effect of the industrial xenobiotics against some biochemical indicators, in view to detect, precociously, the probable significant changes. There are presented the medium, minimum, maximum and median value for the following parameters: total proteins, haemoglobin and glucose for 112 workers exposed or not exposed to specific noxae--benzen, phenol, cyclohexanone. The analysis of the results shows decreased values for some workers, even at the inferior limit, in rapport with the normal values, for the parameters studied. These persons have been directed for complex investigations, in view to determine the causes and to establish the adequate treatment.