The Human Kidney and Urine Proteome Project (HKUPP) was initiated to promote proteomics research in the nephrology field, to better understand kidney functions as well as pathogenic mechanisms of kidney diseases, and to define novel biomarkers and therapeutic targets. The 4th workshop held in September 2009 discussed problems of proteomics analysis for kidney tissues and urine samples and a standard protocol for collection, storage and protein concentration of urine samples was decided upon.