The core roles of mother, sister, and daughter are universal influences in our development as women, and the triangle is an archetypal structure reflecting the interdependent aspects of these influences (see figure 1). It seems likely that this collective experience of women in one or more of these roles informs many of our relationships with other women. Every woman knows the experience of being a daughter. Although not all women have the experience of being a mother or a sister, most women hold some idealized image of mother and sister in their psyche. These experiences or idealizations are often so potent that we project them onto others. They can influence everyday behavior in individual women. The phenomenon of the mother-sister-daughter triangle becomes a lens through which our relationships with other women can be viewed, especially when we are trying to make sense of extreme reactions to another woman—positive or negative, adoration or detestation. To use the mother-sister-daughter lens effectively, you must have some understanding of where you might be caught in the triangle with the other woman to whom you are having a strong reaction. Does she remind you of your mother or sister or daughter? If you can see a connection between how this woman has behaved toward you and an early experience you had, you might come to feel less offended by her. As an example, I felt that a woman I had known professionally, Cheryl, had treated me unfairly, and she had not responded to my requests to discuss the offending incident at the time. Several years went by, and I was not happy to walk into a new organization and see her working there. I felt that I could not trust her because of what happened in the past, and I told other people not to trust her either. I kept my distance from her. I could not see that I was also behaving in an untrustworthy manner by making demeaning comments about her to others. I could only see that she was someone who had done me wrong. After some time in the same organization (and avoiding her), I learned about the mother-sister-daughter triangle in a women’s leadership training course, and I applied it to my relationship with Cheryl. I asked myself whom Cheryl reminded me of in my family. It took some time for me to realize that she reminded me of one of my sisters, who had tried to physically harm me when we were young. I had put Cheryl in the dangerous sister part of the triangle. As soon as I realized I had done that, an amazing thing happened. It was like a curtain lifted and I could see Cheryl for who she really was. I stopped feeling negative about her. We were never able to reconstruct exactly what had happened all those years ago, but she no longer felt untrustworthy to me. She turned out to be a very nice woman who was not my dangerous sister. This was a projection that I had put on her that was not actually about her at all. An excerpt from my book, New Rules for Women, available at Amazon (http://www.amazon.com/dp/0982056982/).]]>