['The dysfunction of the autonomic nervous system is one of the effects of chronic exposure to lead. Heart rate variability (HRV) is a non-invasive method used to estimate the autonomic system. The aim of the study was to estimate HRV in people occupationally exposed to lead.', 'The study group included 43 copper-smelters and 43 healthy subjects matched individually. A 24-hour ECG Holter monitoring was performed in all men.', 'The HRV time analysis in a 24-hour observation, as well as for daily activities (6:00-22:00) and nocturnal sleep (22:00-6:00) showed that pNN50 parameter, an estimator of the vagus nerve function, was significantly lower in copper-smelters than in healthy subjects (p < 0.05). The majority of time and spectral HRV parameters, estimated at 15-min intervals during day- and night-time in the group of lead exposed men, were lower than in the control group (p < 0.05).'] Do [ Effect of chronic lead poisoning on the parameters of heart rate variability ]?