The laboratory development of sol/gel ceramic fibres requires rapid objective means of assessing the mechanical and thermal properties of a product at the earliest stages of preparation. The merits of a simple tumbling test, leading to a fibre friability index, and the Bend Stress Relaxation test, which gives a high temperature creep rating, are demonstrated on commercial Saffil and Safimax alumina fibres and a development Saffil zirconia fibre, each in staple blanket form. Measurements on Alter continuous alumina/silica fibre and Nicalon are also presented. Standard and off specification alumina fibres are readily distinguished by their friability indices which correlate with the fibre strain to break. Saffil and Safimax a lumina a re com parable to Nicalon in terms of creep and superior to Alter. Saffil zircon ia approaches alumina creep performance after post fi ri ng to 1250 degrees C.