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During the course of an investigation of the effects of various thiol reagents upon the rabbit retina (Sorsby, Newhouse, and Lucas, 1957) it was observed that sodium bromoacetate caused histological damage, the details of which are recorded here.Twelve adult rabbits of mixed stock weighing 1[5 to 2 5 kg. received intravenous injections of from 16 to 32 mg./kg. sodium bromoacetate. In three animals the dose was repeated on the following day. The nine survivors were killed for histological examination 3 to 21 days after injection.Two animals received combined injections of sodium bromoacetate (16 mg./kg.) and sodium iodoacetate (16 mg./kg.) and were killed 7 days later. All doses are quoted in terms of sodium salt.The solutions for injection were prepared immediately before use by neutralizing the free acid and making up to volume with phosphate buffer. The eyes were fixed in acid Zenker's solution immediately after death. After removal of the lens, paraffin sections were cut and stained by ordinary haematoxylin and eosin, and by Mallory's phosphotungstic acid haematoxylin. Observations Ophthalmoscopic FindingsRetinal haze, probably due to oedema, was usually observed on the day after injection of doses of 32 mg./kg.; 2 days lter, this effect had diminished and faint pigment clumping was apparent. By 10 days after injection, the pigmentary disturbance in the mid-ventral region had assumed a cobblestonelike appearance; the central fundus showed many yellow spots, but the area above the disc appeared almost normal. No further changes were observed a week later. After the mixtures of iodoacetate and bromoacetate the appearances were similar.Histological Findings (i) After single doses of 16-23 mg./kg. of bromoacetate, three rabbits showed no retinal damage.(ii) After two injections of 23 mg./kg. of bromoacetate, one rabbit showed a very localized loss of visual cells in the area centralis when examined a *