The aim of the study was to investigate Comparision of early and late human milk fortification on growth ,osteopenia and feeding tolerance in preterm newborns in shariati hospital from 2012- 2013. that Inclusion criteria: All pretem infants 28-34 weeks. Exclusion criteria: major congenital anomaly; emergency surjery (PDA ROP,...); infant hospitalize less 7 days ,infant transfer to other care system . This study includes 80 cases that divided on 2 groups of 40 infants 28-34 weeks thus during the study period was 6 weeks, birth weight ,height and head circumfrence, admision weight,Around the abdomen, bowel sounds, gastric lavage.NEC symptoms such as drowsiness, lethargy, biliary lavage, lavage more than 50% milk three hours, increased around abdominal of more than 2cm and stability than the previous feeding period of 6-4 hours and a clear blood in the stool as NEC onset of symptoms and NEC clinical and radiographic signs of disease are reviewed. Another group in the same group are considered as two sides Blind. At the end of the study the rate of weight, height and head circumfrence gain in 4 weeks age,serum calsum,serum phosphor,serum Alkalin phosphatase and serum vitamin -D measure in 6 weeks ago not and two groups are compared