A discussion of chain referral as a method of sampling hard-to-reach populations.

Nursing research often requires inquiry into sensitive topics that involve hidden or hard- to reach populations. However, identifying and sampling these populations for research purposes is often fraught with difficulties. Barriers include society's lack of tolerance of diverse groups, social stigma, concern for issues of confidentiality, and fear of exposure because of possible threats to security. Chain referral sampling techniques are proposed to minimize bias while maintaining privacy and confidentiality. Techniques of chain referral sampling are detailed for use in researching sensitive topics and hidden populations. When carefully planned and executed, this sampling design offers transcultural nurse researchers a reasonable method for accessing and studying special populations that are particularly hard-to-reach.