We have examined changes in endogenous hormones [indole-acetic acid (IAA), gibberellic acid (GA(3)), zeatin (Z) and abscisic acid (ABA)], total phenolic contents and seven major phenolic compounds (gallic acid, +(-) catechin, catechol, chlorogenic acid, o-coumaric acid, rutin and quercetin) in shoot tips of two grapevine cultivars ('Cavus and 'Hafizali') collected during different months, to determine the effects of these endogenous compounds on the survival and subsequent growth of explants in vitro. Shoot tips of grapevine cv. 'Cavus' showed higher explant survival rates than those of 'Hafizali' from all months. Hormone and phenolic compound concentrations also varied depending on cultivar and harvest month. Endogenous compounds showed various correlation coefficients with the survival and subsequent growth of explants. According to our results, the survival and subsequent growth of explants were affected by phenolics and endogenous hormones to various extents. In both grapevine cultivars, shoot tips collected in May exhibited the highest survival rate and growth during the culture period, compared to shoot tips collected in all other months. It may therefore be possible to increase the success of grapevine shoot tip culture by selecting the most suitable collection time.