Current research on usability for mobile commerce has focused on single platforms and very limited aspects of commerce activities. We conducted an exploratory study to examine usability problems and to identify potential research questions concerning wireless solutions for consumer e-commerce. By using cognitive walkthrough and heuristic evaluation methods, we evaluated the usability of ten wireless sites in three platforms: WAP-enabled mobile phones, Palm OS based wireless PDAs, and Pocket PCs running Windows CE operating systems. This article discusses our usability findings pertaining to user tasks, content presentation, search, navigation systems, and the design constraints imposed by form factors. It also provides design guidelines based on our study and examines research implications for wireless interface design.