The use of functional magnetic resonance imaging (fMRI) in cognitive neuroscience has expanded at an amazing rate in the past 10 years. Current research includes increasingly subtle and specific attempts to dissect the cognitive and emotional mechanisms called into play when humans make decisions. The present essay will briefly review some of the general considerations and domains of information needed when one designs fMRI-based experiments. However, the main theme will be the difficulties associated with designing, conducting, analyzing and interpreting such research. Functional MRI is an unusually complicated technique, and there are numerous ways for experiments to go wrong. As well as demanding exceptional care in maintaining the quality of one's own research, this makes the universal problem of evaluating other peoples' research particularly challenging.