BACKGROUND: In many countries and especially in Scandinavia, blood samples drawn in primary healthcare are sent to a hospital laboratory for analysis. The samples are exposed to various conditions regarding storage time, storage temperature and transport form. As these factors can have a severe impact on the quality of results, we wanted to study which combination of transport conditions could fulfil our pre-defined goals for maximum allowable error. METHODS: Samples from 406 patients from nine general practitioners (GPs) in two Danish counties were sent to two hospitals for analyses, during two periods (winter and summer). Transport conditions (mail, courier pick-up, or brought to hospital by public coach), storage time, storage temperature and centrifugation requirements were different in the two counties. Results were tested for deviation from a "0-sample", the blood sample taken, centrifuged and separated at the doctor's office within 45-60 min. This sample was considered as the best estimate of a comparison value. RESULTS: The pre-set quality goals were fulfilled for all the investigated components for samples transported to hospital by courier either as whole blood or as "on gel" after centrifugation, as long as the samples were stored at 20-25 degrees C and centrifuged/analysed within 5-6 h. A total of 4% of the samples sent by mail had mismatched identity, probably due to plasma being transferred to a new tube. CONCLUSIONS: Samples can be sent as unprocessed anticoagulated whole blood if the above mentioned conditions are met. There is no need for centrifugation in the primary sector. Neither mailing of samples with plasma "on gel" nor public transport by coach bus fulfil our analytical goals.