The impact of electromagnetic fields (EMF) on the pineal gland has been described in numerous studies, but many questions still remain unanswered. The aim of the experiment described in this study was to evaluate the effect of EMF on the viability of the pineal gland cells of pig in vitro. Primary culture of the pineal gland cells has been exposed to the influence of an EMF at a frequency of 50 Hz with 1, 2 or 3 hours and for 3 hours every 2 or 3 days. After the experiment, viability of cells was assessed by MTT assay and compared to a control culture not exposed to electromagnetic fields. We noticed that in respect to the control, exposure of the cells to the EMF induced a significant increase in viability of cells at 2 and 3 hours of exposure. After three days of 3-hour exposure to EMF, we observed a significant decrease in cell viability in relation to the control. The results of these studies suggest that EMF can have a significant biological effect on the cells of the pineal gland in a time-dependent exposure to its action.