Twins have long held a special place in medical science as a source of insight into human behavior and genetic links. As a part of its scientific research and efforts to discover more about human behavior, SRI International's Center for Health Sciences established the Northern California Twin Registry in 1995. There are currently more than 2,300 adult twin registrants active in the Registry. Eighteen percent (18%) of these twins are youths aged 18 and under.

Registry members have participated in studies focusing on the pharmacokinetics of nicotine, metabolism of commonly used medications, genetic susceptibility to cancer-causing chemicals, and sleep patterns in young twins.

Do you know any twins?

You can earn money just by referring a pair of identical or fraternal twins to our Registry. If they both join, we'll send you $25.

Become a Member of the SRI Northern California Twin Registry

Identical and fraternal twins (mixed-gender or same-gender pairs) aged 18 and over in the San Francisco Bay Area: We invite you to REGISTER ONLINE or call us at 1-800-SRI-TWIN (1-800-774-8946). By registering, you will be eligible to be invited to participate in studies. Most studies offer payment for your participation.

Identical and fraternal twins (mixed-gender or same-gender pairs) aged 17 and under in the San Francisco Bay Area: Parents or guardians, please call 1-800-SRI-TWIN (1-800-774-8946) to register your twins in the Northern California Twin Registry. (As a precaution, we ask that you do not register a minor online.)

Learn about the Registry

Read about the twin community in our newsletters.

Current Projects

• In partnership with Stanford University, we are examining the genetic and familial aspects of pain sensitivity.

Past Projects

• Examination of the renal clearance of the commonly used prescription medication metformin (used in treatment of diabetes) in identical and fraternal twins to determine the role of heredity
• Comparison of the pharmacokinetics of the medication digoxin (a heart regulator) in identical and fraternal twins to determine whether inter-individual variability is due to genetic factors
• Examination of the extent to which genetics and environment affect sleep in children
• Investigation of the role of genetics in response to cancer-causing agents
• Investigation of whether the predisposition for cigarette smoking is related to how fast the body eliminates nicotine
• Testing of a biometric recognition technique to capture three-dimensional facial images in identical twins

Contact Us
Inquiries or comments on the Registry are welcome and can be directed to

Center for Health Sciences
SRI International
333 Ravenswood Avenue
Menlo Park, CA 94025

SRITWIN@sri.com

Phone: 1-800-SRI-TWIN (1-800-774-8946)
Fax: 650-859-5099