Impurity is the undesirable foreign material which may be toxic or non toxic present in the pharmaceutical substance. Impurity is the substance or the matter which does not form a part of the medicinal or pharmaceutical substance or drugs. Sources of impurities include 1. Raw materials used in the manufacturer. 2. Process used in the manufacturer. 3. Material of the plant. 4. Inadequate storage. 5. Accidental substitutions/deliberate adulteration with spurious/ useless substance. 6. Manufacturing hazards. This ppt also explain Effects of impurities in pharmacopoeial substance.