Patients, policymakers, providers, payers, employers, and others have increasing interest in using personal health records (PHRs) to improve healthcare costs, quality, and efficiency. While organizations now invest millions of dollars in PHRs, the best PHR architectures, value propositions, and descriptions are not universally agreed upon. Despite widespread interest and activity, little PHR research has been done to date, and targeted research investment in PHRs appears inadequate. The authors reviewed the existing PHR specific literature (100 articles) and divided the articles into seven categories, of which four in particular--evaluation of PHR functions, adoption and attitudes of healthcare providers and patients towards PHRs, PHR related privacy and security, and PHR architecture--present important research opportunities. We also briefly discuss other research related to PHRs, PHR research funding sources, and PHR business models. We believe that additional PHR research can increase the likelihood that future PHR system deployments will beneficially impact healthcare costs, quality, and efficiency.