The effects of detergent action on several photochemical and physical properties of chloroplast lamellae have been investigated. The general observations made by other authors who have employed detergents in previous reports have been largely confirmed. It has not however, been found possible to ascribe any of the particular effects which have been observed on the properties of lamellae, to any characteristic of molecular structure and/or polarity of the detergents studied. One detergent of particular interest has emerged from this survey, in the form of G. 711. No other instance is known of any detergent which is an efficient solubiliser of chloroplast lamellae and yet which does not inhibit System II reactions to a high degree at low concentrations of detergent. Of the two photosynthetic photoacts, least is known of the short wavelength System II. The detergent may be of considerable use in future work on the elucidation of the mechanism of the photosynthetic photoevolution of oxygen from water.