Today most of immunochemistry methods for the determination of proteins, peptides, drugs, and many small molecules are fully automated, with good precision, excellent sensitivity and short reaction time. However, inaccuracy due to poor standardization and the presence of interfering substances in biological samples is still a serious and life-threatening issue. Deep knowledge of basic principles of immunochemical methods, sources of analyte-independent interferences and analyte-dependent interferences are very important to understand, detect, reduce and or eliminate the interferences. This book helps to reduce false results, improve patient's care and patient's safety.