Experimental design. Young male rats were entrained to a 12:12 LD photoperiodic cycle for two weeks. Then, they were surgically implanted with E-mitter probes and their body temperature rhythm was recorded for 1 week every 30 seconds. After that, they were diabetic induced with streptozotocin and separated in two large groups: A) late treated and B) early treated with insulin (INS), melatonin (MEL) or a combination of both (INS + MEL). The first group started their treatment 33 days after STZ injection for fifteen days; the second group (B) begun the treatments three days after STZ, for fifteen days. After that, the treatments were interrupted and their rhythms recorded for other fifteen days. At day 41, treatments were resumed for fifteen more days.