Elongated, respirable particles of nedocromil were prepared by its crystallization from N-methyl-2-pyrrolidone (NMP) obtained from an aqueous solution of its sodium salt by precipitation with hydrochloric acid. Aerosols of these particles were recently generated and characterized for their aerodynamic properties (Chan, H.-K.; Gonda, I. J. Aerosol Med. 1993, 6, 241-249). This paper reports the physiochemical properties of the solid form of nedocromil as characterized by polarizing optical and scanning electron microscopies, thermal analysis (DSC, TGA), X-ray powder diffraction, water vapor adsorption isotherms, mass spectrometry, solid state Fourier transform IR and solution 1H-NMR spectroscopies.