University of Southern California Calirornia Twin Program

What is the California Twin Program?
What is the
Twin Program?
The California Twin Program is a non-profit effort conducted at the University of Southern California to collect the basic characteristics of all twins born in California regardless of where they are living currently. Click on the left to learn about the nature and goals of the program and who is eligible to participate.


Why California Twins?
Why California
Here we describe why a twin program is important and why it should be conducted  in California.


First Letter to Eligible Participants
First Letter That
This letter summarizes the history and goals of the program.


About the Questions We Ask
About the
We Ask
This describes the information that is required for participation in the program.

Click here to view the questionnaire

Some Results
Some Results


Check Your


Contact us

Some of the characteristics of native California twins as a group are presented, including details about their zygosity, their geographical distribution and family origins, and their education and occupational similarity. At this site we will periodically provide some figures about different lifestyle practices, medical conditions, and rates of health care utilization among different kinds of twins in California.

Click here to view some recent results from our mammographic density study

About Twins
About Twins Identical Twins on Their Eightieth Birthday Answers to the most common questions asked about twins.



About Twins
Some Other
Twin Websites
The world wide web abounds with interesting information about twins. Here are some sites that we have found. If you have a twins-related website that you would like us to add to the list, go here and submit the site you have found.


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