Potato (Solanum tuberosum L.) responds to heat stress with a shift in partitioning from tubers to shoots. Enzymes responsible for sucrolysis previously have been used as indicators of sink strength and are likely involved in controlling flow of carbon into developing organs. Changes in activity of enzymes involved in sucrose metabolism were investigated in shoots of two potato cultivars that previously were characterized as susceptible and tolerant to heat stress. Enzyme activity of sucrose synthase (SS) and invertases was determined for mature leaves, young leaves, and stems of plants adapted to 21/19 °C, or after transferring plants to 29/27 °C for 3 days. High temperatures resulted in a nonsignificant increase in activities of SS, acid, and neutral invertase in young growing leaves but not in stems or mature leaves. The combined activity of the two invertases was ≈40 times higher than SS activity in young leaves. There was no temperature genotype interaction with regard to these enzymes in the tissues investigated. A previously reported increase in activity of sucrose-phosphate synthase in mature leaves of plants subjected to high temperature was reversed after these plants were returned to a normal growing temperature.