A process is provided for preparing novel crystalline forms, namely selectively and consistently preparing the H2-1 dihydrate crystalline form, the H2-2 dihydrate crystalline form, the N-3 anhydrate crystalline form and the MTBE solvate crystalline form of the IKur compound (2S)-1-[[(7R)-7-(3,4-dichlorophenyl)-4,7-dihydro-5-methylpyrazolo[1,5]pyr- imidine-6-yl]carbonyl]-2-(4-fluorophenyl)pyrrolidine. The process includes preparation of the H2-1 and H2-2 forms which are used in preparing the N-3 anhydrate form which is particularly stable and has suitable flow properties and desired particle size. Novel H2-1 dihydrate and H2-2 dihydrate forms, the N-3 anhydrate form and the MTBE solvate form of the above IKur compound, pharmaceutical compositions containing such novel forms and a method for preventing or treating arrhythmias including atrial fibrillation and IKur related conditions employing such novel forms are also provided.