We have studied the Raman modes in HgBa2CuO4+δ crystallites through polarized Raman measurements. The Raman peaks at 158 and 592 cm-1 are assigned to be the Ba A1g mode and the O(2) A1g mode respectively. This is in reasonable agreement with the results of LDA total-energy phonon calculations of HgBa2CuO4+δ. To clarify symmetry and site assignment for the mode near 570 cm-1, we studied its behavior at elevated temperatures. Together with a thermogravimetric analysis (TGA), it is found that the 570 cm-1 mode is not related to the O(3) 'interstitial' oxygen as suggested by some authors. However, the polarization dependence of the 570 cm-1 mode shows no conclusive sign of Eg symmetry contrary to our previous speculation.