The present invention provides substantially pure desloratadine having an HPLC purity greater than 99.5% and having an absorbance less than 0.15 Au at 420 nm for a 5% w/v solution in methanol, which does not show a peak for an impurity at a relative retention time in the range from about 0.85 to about 0.99 (relative to desloratadine appearing at a retention time of 25.+-.5 minutes), which is greater than the discard limit set at less than 0.025% of the total area, when tested according to an HPLC method performed using a Hypersil BDS C.sub.8 column (15 cm.times.4.6 mm, 5 .mu.m particle size) with the following parameters: TABLE-US-00001 Mobile phase: Buffer solution having a pH of about 3, methanol and acetonitrile in a volume ratio of 8:1:1. Injection volume: 20 .mu.l Flow rate: 1.5 ml/minute Run time: 75 minutes. Discard limit: Set at less than 0.025% of total area The present invention also provides a process for the preparation of substantially pure desloratadine by the process comprising acidic hydrolysis of a compound of formula 3 where R is selected from COR.sub.1, COOR.sub.1 wherein R.sub.1 is selected from branched or linear alkyl (1-6 C), cycloalkyl, alkenyl, alkynyl, aryl, aralkyl and their substituted analogs; and their substituted analogs with a strong organic acid or a mineral acid. ##STR00001##