To evaluate the efficacy of a measure able to compare energy intake from parenteral and enteral nutrition we documented growth patterns in a group of VLBW infants treated with parenteral nutrition (PN). To analyze comparative energy intake from the two sources we expressed a percentage of both parenteral and enteral calories: the former (RCP%) related to an optimal value of 85 non protein calories and the latter (RCE%) to an optimal value of 150 total calories. Total energy intake was planned on the RCT% (RCP% + RCE%). We studied 75 VLBW infants with a mean BW of 1040 g and a mean GA of 29.5 weeks. The mean duration of PN was 25.8 +/- 10.4 days. The initial weight loss (10.2 +/- 5.3%), the time to regain BW (5.5 +/- 4 days) and the day of lowest weight (5.2 +/- 1.6 day of life) were in the normal range; the subsequent growth rate resulted 25.9 +/- 9.2 g/kg/die and did not change for different GA or BW. Growth pattern about head circumference and length were above the third percentile. The mean age of RCT% = 100% was 11.4 +/- 4.8 days of PN; this value was higher for the more premature infants. Severe metabolic abnormalities were not detected. Our observations show the efficacy of the RCT% as index of energy from both enteral and parenteral source during PN: the growth pattern seems to be quite satisfactory without any severe metabolic complication.