Efforts of the SIMSAM network include to enhance the quality of register-based research and to support methodological developments. SIMSAM contributions to a dedicated supplement of Scandinavian Journal of Public Health (SJPH, volume 45, Issue 17, July 2017) is an important part of these endeavors. The SIMSAM SJPH supplement includes 11 papers, stemming from ongoing research activities within the SIMSAM network, and gives several examples of important practical aspects that researchers should consider when using Swedish and Nordic registers, as well as data quality, discussions of appropriate study designs and analytical strategies. The presented research is diverse and includes studies of immigrant populations, early-life determinants of childhood health and cardiovascular outcomes, as well as studies on effects of job training on return to the labor market and how social background affects educational choices among school children A review of both commonly used and more novel register-based study designs is presented, and further illustrated in several of the other papers in the supplement. Among analytical approaches, examples of quite different uses of propensity scores and related matching techniques are provided, reflecting the increased popularity of propensity scores in observational research in general as a strategy for control of confounding and selection effects.