An unknown, but significant subgroup (perhaps the majority), of patients who have undergone chemotherapy treatment for their cancer report a subsequent decline in cognitive performance (e.g., difficulty in balancing a checkbook; forgetting or mixing up names of friends or relatives, etc.). The condition has been termed chemo fog, chemo brain, or some similar term to reflect the fact that the symptoms are usually difficult to describe and involve domains of cognition such as attention, concentration, memory, speed of information processing, multitasking, or ability to organize information. The deficits are reported to persist. The magnitude of the negative impact on quality of life depends, as does the condition itself, on multiple and varied factors. This chapter relates the experience of one patient.