Post-chemotherapy cognitive impairment describes the cognitive impairment that can result from chemotherapy, with approximately 20% to 30% of people undergoing chemotherapy experiencing some level of cognitive impairment after treatment. This phenomenon was first discovered in an evaluation of a large group of breast cancer survivors who complained of problems with memory, fluency, and other mental abilities. Although the causes of post-chemotherapy cognitive impairment have been debated, recent studies have confirmed that post-chemotherapy cognitive impairment is a real, measurable side effect of chemotherapy and is seen in some patients. While any cancer patient may experience temporary cognitive impairment during chemotherapy, patients with PCCI continue to experience these symptoms long after chemotherapy is complete. PCCI is most often seen in patients treated for breast cancer, ovarian cancer, prostate cancer, and other reproductive cancers, as well as other cancers that require aggressive chemotherapy. The clinical significance of PCCI is significant, given the growing population of long-term cancer survivors, many of whom have been treated with aggressive doses of chemotherapy drugs, or have had chemotherapy as an adjunct to other forms of treatment. In some patients, fear of PCCI may influence treatment decisions. The magnitude of chemotherapy-related cognitive changes and their impact on activities of daily living is uncertain. The body systems most affected by chemotherapy drugs include visual and semantic memory, attention, and motor coordination. These effects may affect a chemotherapy patient’s ability to understand and make decisions about treatment, perform at school or work, and can reduce quality of life. Survivors often report difficulty multitasking, understanding what they have just read, following the development of a conversation, and recalling words. Breast cancer survivors treated with chemotherapy may have more difficulty performing tasks than survivors treated with surgery. The brains of cancer survivors treated with chemotherapy physically shrank, while the brains of people treated with surgery alone did not. Cognitive impairment after chemotherapy comes as a surprise to many cancer survivors. Often, survivors think their lives will return to normal once the cancer is gone, only to find that the lingering effects of post-chemotherapy cognitive impairment are hampering their efforts. Working, communicating with loved ones, and doing everyday tasks—all of these can be extremely difficult for a brain with a weakened mind. Although post-chemotherapy cognitive impairment seems temporary, it can be long-lasting, with some cases lasting 10 years or more.