Mortality of calves is not only costly for dairy cattle farmers, but it is also a problem related to animal health and welfare.This study was carried out to estimate genetic parameters of mortality in female calves in different age groups until an age of 760 d (nearly first calving). Records of 123256 female calves born in the years 1998 to 2011from 60 Holstein dairy herds in Isfahan province were used. Six age periods of mortality: 1 to 30 d, 31 to 180 d, 181 to 365 d, 366 to 760 d, d 1 to 450, and the full period 1 to 760 d were considered. Records of animals slaughtered or exported within a defined period were set to missing values, whereas their records were kept for preceding periods. After data editing, records of 52311 female calves born in the years 1998 to 2009 from 50 Holstein dairy herds were used. The pedigree consisted of 519 sires and 993 animals, and for the estimation of genetic parameters, linear sire model and threshold sire model were applied. Effects accounted for were fixed effects of herd-year- season, number of dam’s parity, calving ease, and twin as well as the random effect sire. Mortality rates were 2.17, 3.42, 1.98, 4.17, 8.2, and 12.4% for the six mentioned periods, respectively. Observed heritabilities were low, and ranging from 0.3 to 2%. Heritability estimates by threshold models were 2 to 3 times greater than linear model and ranging from 0.6 to 2.3%. Heritabilities by threshold and linear models were distinctly higher for 180 to 365 d. The genetic correlations between six different periods ranged from 0.22 to 0.82. Genetic correlations between 1 to 30 d and other periods were lowest, and indicating that different genes control mortality in the early and late postnatal stages. The Spearman rank correlations for breeding values of these bulls estimated by linear and threshold models were high and indicating that only small changes in ranking of bulls occurred depending on the evaluation method. Because of lower frequency and higher heritability and genetic coefficient of variation for mortality in 180 to 365 d and also the high genetic correlations between this period and 31 to 180 d and 366 to 760 d, the period of 180 to 365 d could be taken into account for future developments aimed at routine evaluations. Key words : calf mortality- linear model- threshold model- genetic parameters- spearman rank correlation