Storage is one of the most important and, at the same time, most difficult stages in potato production and potato economy. During long-term storage, potato tubers are affected by processes leading to quantitative changes. The present three-year field experiment (2003-2005) investigated the effect of varied mineral fertilization (N, K and Mg against the fixed P dose) and storage (3 and 6 months) on the occurrence of quantitative potato tuber losses. The research involved mid-early cultivars: Bila and Triada. The samples were stored in a storage chamber for 3 and 6 months (temperature +4ºC, relative humidity 95%). The present research shows that natural losses were affected by all the experimental factors. The K and Mg fertilizer doses significantly decreased the amount of fresh weight losses as compared with the control; as for potassium, the most favourable in that respect was the dose of 160 kg K2O ha–1, and for magnesium – 60 kg MgO ha–1. Nitrogen fertilization, on the other hand, demonstrated a negative effect on the amount of losses throughout the storage period. The highest fresh weight losses occurred after 6 months of storage and for the nitrogen, potassium and magnesium fertilization experiments they reached 8.9, 6.4 and 7.3%, respectively. The best storage life was reported for cv. Triada potato tubers – potassium fertilization and cv. Bila – magnesium fertilization.