Head-mounted displays (HMDs) have the potential to overcome some of the technological limitations of currently existing automotive head-up displays (HUDs), such as the limited field of view and the restrictive boundaries of the windshield. In an initial study we evaluated the use of HMDs in cars by means of a typical HUD visualization, using a HUD as baseline output technology. We found no significant differences in terms of driving performance, physical uneasiness or visual distraction. User statements revealed several advantages and drawbacks of the different output technologies apart from technological maturity and ergonomics. These results will hopefully inspire researchers as well as application developers and even might lead us to novel HMD visualization approaches.