Changes in soil water regime during vegetative growth and yield production of potato crop was not equally affected by soil water depletion. Concerning to yield production the results show that the soil water depletion effect are closely related to intensity and duration of water deficits and stage of plant growth in which they occurs. So, it was stablished that during the stage of tuberization and tuber development, the plant exhibited higher sensibility to water deficiency than in the initial or final stage of plant growth. On the other hand, moderate deficits (-1.0 bar of soil water matric potential) occurring in the initial stage of plant growth did not have any effect in tuber yield. This was attributed to the resumption of growth in the following stage. However, when a more severe water deficiency occurred (-5.0 bars of soil water matric potential), it was not observed the resumption phenomenon. In this case, an irreversible decrease in growth had the effect of decreasing yield. Soil moisture depletion in the final growth stage, about 60 days after plant emergence, did not decrease tuber yield, which increased plant water efficiency. When water supply was suppressed in this stage, the senescence was hastened in 16 days when compared to the other treatments with higher levels of soil moisture. As was evidenced, the vegetative growth is not an absolute index of the potato yield production.