In daily practice, collecting urine for the determination of microalbuminuria may take place in various ways and several different procedures are often used side by side in one institution. Ideally, the collection of urine should be as simple as possible for the patient, without losing diagnostic value. Having considered the pros and cons of the various procedures, we recommend measurement of the albumin-creatinine ratio in the 1st morning urine for both diagnosis and follow-up. This ratio is reported in gram of albumin per mol of creatinine and sex-dependent cut-off values must be used when interpreting the results: there is microalbuminuria above 2.5 g/mol for men and above 3.5 g/mol for women. If microalbuminuria is detected, the investigation should be repeated at least twice in a period of a few months in order to establish the degree of microalbuminuria.