To evaluate the opportunity of exercise electrocardiography (ECG) in the sanitary surveillance of workers with physical strain, we estimated the energy consumption of the duties of 22 electrical workers (males; age: 35-56 years). They subsequently underwent Treadmill exercise ECG, determining for each worker the maximal METs (multiples of basal metabolism) and the critical potency (P(CRIT)). In one subject, myocardial ischemia arose 9 minutes after the beginning of the test. The others interrupted the test after 7-13 minutes for tiring; 5 of them showed ventricular extra systoles, paired or isolated. Twelve subjects presented arterial hypertension, at rest and/or during exercise. Ergonomic analysis revealed that the occupational duties were between 1.5 and 8.0 METs. The energy consumption of the job on the whole was 4-6 METs (medium intensity). The maximal METs reached by the examined subjects were between 8.8 and 15.6; however, only 11 workers went reassuringly over the 4 METs required by duty analysis at P(CRIT). One subject was declared unfit for the job, and a judgement of partial idoneity was expressed for 3 workers. Preventive and therapeutic indications were given to 12 subjects. Aerobic training was suggested to 10 workers. The study indicates that an ergonomic evaluation is advisable for the most energy consuming occupational duties. In such cases, the sanitary surveillance should include a cardiologic assessment with exercise ECG, reproducing the physical strain of the specific job.