Reduced heart rate variability (HRV) is associated with the elevated mortality rate in patients with cardiovascular disease. Risk factors, in terms of the negative impact on the cardiovascular system of workers of oil production include noise, vibration, the severity of the labor process, climate, lighting, and various chemicals presenting in the working area (the total of various hydrocarbons, including aromatic hydrocarbons, disulfide sulfur). HRV indices were recorded daily by Holter monitoring. Employees with the work experience at oil production from 10 to 20 years were established to have a statistically significant increase in tone of the sympathetic nervous system, characterized by the decline ofpNN50 by 2.2 times and the increase of the vagal tone, characterized by an increase in SDANN by 1.4 times and SDNN - by 1.3 times. A significant dependence of the probability of the increasing of the tone of the sympathetic nervous system from work experience was established. Thus, the impact of hazards of oil-producing enterprise is associated with prognostically unfavorable changes in HRV. These changes may exacerbate hypertension in employees, which requires measures for the primary prevention of cardiovascular diseases.