Colonic pseudo-obstruction is characterized by non-mechanical chronic colonic dilatation. It is an infrequent entity that can be provoked by multiple causes, among them pharmacological. We present the case of a 74-year-old female psychiatric patient who presented abdominal bloating, diarrhea, intense electrolytic alterations and marked radiographic colonic dilatation after treatment with a neuroleptic (zuclopenthixol decanoate). Organic obstruction and other causes were ruled out and the final diagnosis was chronic colonic pseudo-obstruction secondary to the use of neuroleptics. Cisapride (20 mg/8 h) produced a slight improvement in symptoms but colonic dilatation was permanent.