The aim of this chapter is to focus on the analysis of abnormal constituents in urine. Substances which are not present in easily detectable amounts in urine of normal healthy individuals but are present in urine under certain diseased conditions are said to be ‘abnormal’ or ‘pathological’ constituents of urine. Analysis of these abnormal constituents aids in the diagnosis of many diseases. Many of these pathological constituents are present in trace amounts in normal urine but they escape detection due to the low sensitivity of the methods employed. The concentrations of these constituents in urine are increased markedly in different pathological conditions. This chapter covers the physical characteristics in pathological conditions, chemical constituents, and analysis of abnormal urine.