In this study, dissolution of Eri (Philosamia ricini) cocoons in different solutions was investigated and compared with Nang-Lai variety (Bombyx mori) cocoons. The Lithium Bromide (LiBr), calcium nitrate (Ca(NO₃)₂), Zinc chloride (ZnCl₂), Lithium thiocyanate (LiSCN·xH₂O), 85% phosphate and mixture (calcium chloride (CaCl₂)/Ethanol/H₂O; 1:2:8) solution systems were used. Efficiency of the dissolving solution was examined by measuring the percentage of dissolved silk. It was found that the Nang-Lai silk was completely dissolved in all solutions, whereas, Eri silk was slightly dissolved, except for 85% phosphate solution. The Fourier transform infrared spectroscopy (FTIR) spectra of the Eri silk film composed of β-sheet form than Nang Lai silk film. With thermogravimetric analysis, the Eri silk film showed two stages of thermal decompositions while the Nang-Lai silk was a single stage. In conclusion, thermal stability of the Eri silk was higher than the Nang-Lai silk. © 2009 Asian Network for Scientific Information.