The following results were obtained from experiments with 23 clinically intact weaned piglets, aged between five and six weeks (18 animals) or eight weeks (five animals), which had received three intragastric applications of crude enterotoxin (culture filtrate supernatant of Escherichia coli O149:K91(B)K88(L):. 1. Twelve animals (52 per cent) responded to enterotoxin application by temporary outbreaks of diarrhoea (1-8.5 hours) following differentiated latencies (2.5-10 hours). No diarrhoea was recorded from eleven piglets (48%) which had received the same doses of enterotoxin. 2. No signs of a systemic disease were clinically recordable after enterotoxin administration from 22 (96%) animals, no matter whether diarrhoea had developed or not. Respiration, temperature, heart rate, and haematological values were unchanged. Feed and water intake were normal. No exsicosis was observed. All animals exhibited lively behaviours and activity. The conclusion drawn regarding the pathogenesis of the gastrointestinal form of coli-enterotoxaemia, with reference to the authors' own earlier findings, is that in this disease parenteral endotoxin effects (following endotoxin resorption) seem to coincide with enteral enterotoxin effects.