Provided are the following novel crystals of 2-{4-[N-(5,6-diphenylpyradin-2-yl)-N-isopropylamino]butyloxy}-N-(methylsulfonyl)acetamide (hereinafter, referred to as "compound A"):I-form crystals of the compound A which give an X-ray powder diffraction spectrum having diffraction peaks at least at diffraction angles (2θ) of 9.4º, 9.8º, 17.2º, and 19.4º；II-form crystals of the compound A which give an X-ray powder diffraction spectrum having diffraction peaks at least at diffraction angles (2θ) of 9.0º, 12.9º, 20.7º, and 22.6º； andIII-form crystals of the compound A which give an X-ray powder diffraction spectrum having diffraction peaks at least at diffraction angles (2θ) of 9.3º, 9.7º, 16.8º, 20.6º, and 23.5º.
