Several fragments of Japanese ancient fabrics, most of which have been attributed to the Shoso-in Repository Fragments (8th century), were examined non-destructively in order to confirm some latent properties of these fragments. Analysis of fibrous material was carried out using the FT-IR-ATR method. Although these fragments have already seriously deteriorated, their IR spectra coincide closely with those of modern silk fibres. Dyeing mordants applied to these fragments were analysed by means of energy dispersive X-ray fluorescence (EDXRF). Several elements, S, Si, K, Ca, Al, P, Fe, Mn and so on, have been detected from the fragments, some of which are particularly rich in aluminum content. Compared with the EDXRF data for the mordanted reference samples, the fragments examined were shown to be mordanted with certain plant-ash. Also, it was surmised that the use of Fe mordant was probably avoided in preparing these fragments, suggesting that ancient Japanese dyers had already been aware of some kind of plant-ash which brings about a dull colour tone on dyeing. In an attempt to identify dyes applied to these fragments, laser-induced fluorescence and optical reflection spectra were measured for both samples, i.e. the fragments and reference fabrics dyed with natural dyes using a traditional technique. Identification was performed by a comparison of various spectral characteristics for both the fragments and reference samples. Shikon and/or Japanese madder have been identified for purple and/or reddish-purple coloured fragments. Combination dyeing of kihada (or wo-ren) and indigotin has been determined for the fragment of yellowish-green colours. The possibilities and limits of these non-destructive methods available for the analysis of ancient fabrics are also discussed. It is proposed that a combination of several non-destructive methods is needed to be applied in cases where some valuable dyed samples are concerned.