Objective: The purpose of the study is to elucidate the relationships and inter-relatedness of specific structure, process, and outcome elements contributing to harmful medication errors for the vulnerable people who reside in nursing homes by exploring the inter-relationships between structure and process factors in relationship to medication errors and medication errors associated with harm.Methods: The Medication Error Quality Initiative-Individual Error (MEQI-IE) Data for North Carolina nursing homes for FY 2007 was used for analysis. A multivariable model was used which controlled for facility and resident characteristics, phases of the medication use process, reported causes of the error, primary type of error, personnel involved, and number of medications.Results: Ownership status does not directly impact the number of medication errors reported or a more harmful error being reported. Chain affiliation was found to interact with ownership status; a not-for-profit nursing home that is a member of a chain is predicted to have half the rate of medication errors that a for-profit nursing home that is not part of a chain has. Prescribing errors are associated with harm more often than administering errors during the medication use process; and a dose omission error is less likely to be associated with harm than a wrong dose error.Conclusions: Over two-thirds of the nursing homes reported a medication error during the first seven days of a resident's admission. Chain affiliation interacts with ownership status and is associated with a decrease in incidence rate of reported medication errors. Medication errors during the administration phase account for one third of the errors, but prescribing errors, which account for only 4.8% of all errors, are associated with more harmful events. Wrong dose errors are associated with harm twice as often as dose omissions even though dose omissions were reported in over one third of the errors. Almost one half of the wrong dose errors occurred during the documenting phase with 42.7% a recording issue. The processes surrounding and related to documentation and recording of the medication use process are critical to medication safety for residents during their first seven days of admission into the SNF.