Fever in cancer patients is often due to the following causes: evil qi and toxity stagnancy, disorders of qi and blood, deficiencies of zang and fu organs, and the disorder of yin and yang. The treatments given to cancer patients with a fever are according to five: (a) Excessive inner heat and toxicants: remove heat and the toxicant, induce purgation. We use Cheng-Qi-Tang plus Qing-Wen-Bai-Du-Yin. (b) Tangle of damp and heat, and qi stagnancy: remove damp and heat, smooth the qi channel. We use Gan-Lu-Xiao-Du-Dan or San-Ren-Tang. (c) Obvious blood and heat stagnancy: remove heat and blood stasis. We use Xue-Fu- Zhu-Yu-Tang. (d) Deficiency of spleen qi, inner heat caused by a yin deficiency: nourish spleen qi and yin to remove the inner heat. We use Bu-Zhong-Yi-Qi-Tang or Xiao-Jian-Zhong-Tang. (e) Prominent yin deficiency and hectic fever: replenish yin and remove inner heat. We use Qing-Hao-Bie-Jia-Tang or Chai- Qian-Mei-Lian-San. The pathogenesis of fever in cancer patients is complicated. We can see both deficiency and excess in one differentiation. Therefore, we must make sure of it, then we can get the most effective treatment.