Background: Australia has a statutory incident reporting system for radiopharmaceutical maladministrations, but additional research into registry data is required for the purpose of quality improvement in nuclear medicine. Aims: We (i) used control charts to identify factors contributing to special cause variation (indicating higher than expected rates) in maladministrations and (ii) evaluated the impact of heterogeneous notification criteria and extent of underreporting among jurisdictions and individual facilities, respectively. Methods: Anonymised summaries of Australian Radiation Incident Register reports permitted calculation of national monthly maladministration notification rates for 2007-2012 and preparation of control charts. Multivariate logistic regression assessed the association of population, insurance and regulatory characteristics with maladministration notifications in each Australian State and Territory. Maladministration notification rates from two facilities with familiarity of notification processes and commitment to radiation protection were compared with those elsewhere. Results: Special cause variation occurred in only 3 months, but contributed to 21% of all incidents (42 of 197 patients), mainly because of 'clusters' of maladministrations (n = 24) arising from errors in bulk radiopharmaceutical dispensing. Maladministration notification rates varied significantly between jurisdictions (0 to 12.2 maladministrations per 100000 procedures (P < 0.05)) and individual facilities (31.7 vs 5.8 per 100000; χ2 = 40; 1degree of freedom, P < 0.001). Conclusions: Unexpected increases in maladministration notifications predominantly relate to incident 'clusters' affecting multiple patients. The bulk preparation of radiopharmaceuticals is a vulnerable process and merits additional safeguards. Maladministration notification rates in Australia are heterogeneous. Adopting uniform maladministration notification criteria among States and Territories and methods to overcome underreporting are warranted.