Due to significant absorption in the near infrared in pure L-arginine phosphate monohydrate (LAP) deuterated LAP (dLAP) crystals have been grown using heavy water (D2O) as a solvent by a slow cooling technique. The growth conditions for the growth of monoclinic dLAP crystals are optimized by adjusting the growth parameters, Such as pH, temperature etc. The grown crystals are morphologically compared with the Pure LAP crystals. For extending the shelf life of the dLAP solution, 1 wt% of potassium fluoride has been added in the solution and the LAP, dLAP and dLAP:KF solutions are comparatively examined. The variation of lattice parameters of dLAP crystal with pure LAP is found from the X-ray powder diffraction studies. The thermal behaviour and Molecular vibrations of dLAP are reported from DT&TG and FTIR studies. (C) 2002 Elsevier Science B.V. All rights reserved.