Nowadays, complementary and alternative medicine (CAM) is popular all over the world. Billions of dollars are spent in this booming business. For several reasons, young, female, educated, and higher socioeconomic class cancer patients, in particular, have shown interest in these agents. Unfortunately, besides direct (and sometimes serious) side effects, several CAM ingredients are capable of interfering with the metabolism of concurrently used drugs, which may render the therapeutic outcome of the subscribed drug unpredictable. In the case of anticancer drugs, with their usually narrow therapeutic window, this may have dramatic consequences and can lead to unacceptable toxicities in some cases or decreased therapeutic activity in others. Therefore, cancer patients should be warned for these possible interactions and be advised to discuss CAM use openly with their treating physician. The general concept that natural products are harmless should thus be changed into a more realistic and responsible attitude. A tightened legislation and regulation (including Internet advertising and sales) could play a crucial role in this awareness process. This should finally enable safe exploration of the potential advantageous aspects of CAM, while living with cancer.