The structures of two compounds, AH₁ and AH₂, isolated from agalwood "Jinko" were studied. AH₁ was obtained as needles having a melting point different from that of agarotetrol (powder) isolated and characterized by Yoshii et al. However, the carbon-13 nuclear magnetic resonance (¹³C-NMR) data and [α]_D values of the two compounds were identical, and AH₁ was concluded to have the same structure, including stereochemistry, as agarotetrol. The half-chair conformation of the hexenyl ring moiety assumed by Yoshii et al. was confirmed by detailed analyses of the proton nuclear magnetic resonance (¹H-NMR) and 2D-COSY spectra.AH₂ was assigned the structure (5S, 6R, 7R, 8S)-2-(2-phenylethyl)-5e', 6e, 7e, 8'e-tetrahydroxy-5, 6, 7, 8-tetrahydrochromone, a stereo-isomer of agarotetrol (7S, 8R), on the basis of the ¹H-NMR, X-ray analysis and circular dichroism (CD) spectral data. It was named isoagarotetrol. The hexenyl ring moiety of isoagarotetrol was found to have a half-chair conformation identical to that of agarotetrol in the crystalline state as well as in solution.