In this paper we present novel input devices that combine the standard capabilities of a computer mouse with multitouch sensing. Our goal is to enrich traditional pointerbased desktop interactions with touch and gestures. To chart the design space, we present five different multitouch mouse implementations. Each explores a different touch sensing strategy, which leads to differing formfactors and hence interactive possibilities. In addition to the detailed description of hardware and software implementations of our prototypes, we discuss the relative strengths, limitations and affordances of these novel input devices as informed by the results of a preliminary user study. ACM Classification: H.5.2 [Information interfaces and presentation]: User Interfaces. – Input devices and strategies; Graphical user interfaces. General terms: Design, Human Factors, Algorithms