Statistical strength and size effect of Nicalon fibre bundles are studied. The Weibull type of statistical theory underlying predictions of bounding Nicalon fibre bundle strength is presented and discussed. The relationship of bundle strength to single Nicalon filament strength and a model explaining the correlation are also discussed. The predicted values for Nicalon fibre bundles were in close agreement with the experimental data. Characterization of Nicalon fibres or bundles provides an insight into the ultimate mechanical performance of ceramic-matrix composites.