Danfoss Drives - one of the largest producers of frequency converters in the world - is in a situation like many others: it has to produce a number of product series with an increasing number of variants, while at the same time decreasing time-tomarket and keeping development costs low. As part of the strategy to master this challenge, Danfoss Drives decided to reduce software development efforts by migrating to a product line approach. This paper describes the approach Danfoss Drives took to successfully introduce Software Product Line Principles into its organization.