Is firm growth more persistent for young or old firms? Theory gives us no clear guidance, and previous empirical investigations have been hampered by a lack of detailed data on firm age, as well as a non-representative coverage of young firms. We overcome these shortcomings using a rich dataset on all limited liability firms in Sweden during 1998–2008, covering firms of all ages and information on registered start year. Sales growth for new ventures is characterized by positive persistence, which quickly turns negative as firms get older. Young firms are more likely to have two consecutive periods of positive growth. While new firms experience an early burst of sustained growth, older firms have more erratic growth paths.