Systematic modern animal experimentation was established by Bernard Claude who wrote “An Introduction to the Study of Experimental Medicine” in 1865. At this point, the public was already asking that the pain and distress of experimental animals be reduced. For this, scientists, William Russell and Rex Burch in 1959 proposed the principles of alternatives to animal experimentation, the “3Rs”. Since that time, animal welfare advocates have promoted the 3Rs concept in biomedical research communities. However, cruel animal experiments have continued and there are reports of radical extremists showing their opposition by invasion, arson, theft and even bombing of institutions involved, resulting in killing of the animals. SHAC, one extremist group believed to be animal welfare activitists was recognized as a terrorist group after the 9.11 tragedy in USA and the government viewed their activities very seriously. In 2001, British animal extremists invaded Japanese universities and stole laboratory resources; one individual was arrested and sentenced to prison for three years; Japanese who assisted in the incident were arrested and one was sentenced for one year. In 2006, SHAC USA members were prosecuted and sentenced for up to 6 years for their terrorism activities including arson. We need to consider the background of these activities which are financially supported by animal welfare advocates. The way we, as scientists who conduct such experiments can respond is by promoting alternatives to this experimentation. In Japan, the animal welfare law was revised in 2005 stressing the importance of 3Rs in scientific activities with animals. The promotion of 3Rs should be strengthened in the pharmaceutical community.