maximum yield of imatinib mesylate methanesulfonic acid can be added to the solution of imatinib free base in chlorinated solvent preferably between about 5 u00b0 c to reflux temperature more preferably between room temperature to reflux temperature most preferably methanesulfonic acid is added at room temperature then the precipitated imatinib mesylate form h1 is collected by filtration or centrifugation in accordance with the present invention an another process is provided for preparation of imatinib mesylate form h1 a mixture of imatinib mesylate and a chlorinated solvent is stirred for about 10 hours to 48 hours and imatinib mesylate form h1 is isolated examples of chlorinated solvents are chloroform methylene dichloride ethylene dichloride and a mixture thereof preferable solvents are chloroform and methylene dichloride imatinib mesylate in a previously known crystalline or amorphous form may be used in the process imatinib mesylate hydrate obtained by the process described below may also be used particularly u03b1 form u03b2 form or amorphous imatinib mesylate may be used preferably the mixture of imatinib mesylate and a chlorinated solvent is stirred between about 5 u00b0 c to reflux temperature more preferably between room temperature to reflux temperature for about 24 hours to 48 hours then imatinib mesylate form h1 is collected by filtration or centrifugation in accordance with the present invention there is provided a novel hydrate of imatinib mesylate the water content of the hydrate of imatinib mesylate is between 2 0 to 3 2 by weight of hydrate of imatinib mesylate typically between 2 2 to 2 9 by weight of hydrate of imatinib mesylate the amorphous form of imatinib mesylate hydrate designated as amorphous imatinib mesylate.