Four-colour photometry of hydrogen-deficient stars and related objects Stromgren uvby photometry of hydrogen deficient and helium-weak starssuggests that the 'extreme helium' (= 'hydrogen deficient') stars whichhave been well observed are all variable, probably in a complex way.Previously observed short-term variability of HD 160641 and long-termvariability of HD 168476 are confirmed. There is no evidence forvariability in the intermediate helium stars or the helium-weak stars.
