The behavior of twenty-three hybrid lactating sows from the 1st, 2nd, 3rd and 4th parity orders maintained in a warm environment was evaluated during the four periods of Day 17 of lactation (6 to 12 a.m. (P1), 12 a.m. to 6 p.m. (P2), 6 p.m. to 12 p.m. (P3), and 12 p.m. to 6 a.m. (P4)). The frequency (n) and duration (min) in which the sows remained lying down (SE), in lateral (DL) or ventral (DV) decubitus, standing up, but idle (OEP) or in activity at the feeder or drinker (PACB) was detected. Evaluations in relation to behavior during lactation included the frequency, type and duration of sucking terminated by the sow (ATPOR), terminated by the piglets (ATLEI) or successfully concluded. Parity order (OP) influenced the time used in DL and in PACB. There was a significant effect (P<0.05) of the period of the day for all variables except OEP. In connection with this, it can be concluded that all sows became more restless during the warmest periods of the day, reducing the frequency of posture in DL and the number of suckings by the piglets.