Genetic parameters and genetic trend of productive life (PL) in Iranian Holsteins have been estimated using survival analysis techniques. A Weibull mixed sire-maternal grandsire survival model was used to estimate genetic parameters and genetic evaluation of sires for productive life of their daughters. Data from 423578 lactation and 172551 productive life of cows with first calving from 1987 to 2004 were used for the analysis. 44.54% of data was right censored. Length of productive life was defined as the number of days from first calving until culling or censoring. Estimated heritability were 0.063 and 0.180 on log and original scale for functional and 0.059 and 0.164 for true productive life, respectively. Herd-year-season, milk production, lactation and stage of lactation, Holstein Friesian gene percentage and age at first calving had very significant effect on PL (p<0.01). Relative risk of culling increased as age at first calving increased. The most important change in log likelihood was observed for milk production. Risk of culling for low producing cows (milk production below 1.5 standard deviation of herd-year average) were four times greater than that for high yielding cows. Predicted transmitting ability for functional productive life, expressed as relative risk ratios and ranging from 0.45 to 1.74, indicates that the risk of culling for daughters of the worst sires was four times greater than that for the best sires and nearly 80% greater than that for the average sires. A large variation was observed among sires for their daughter’s longevity, thus selection of sires might result in suitable genetic gain. Estimated genetic trend was 0.06(genetic standard deviation) per year.
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