CONTEXT Maintenance fluid therapy is a protean topic but is clinically often mismanaged. Our teaching of medical students led us to suspect that textbooks provide limited information about the topic, so we set out to verify this possibility by reviewing the content of books written in English that covered perioperative care. METHODS We reviewed publishers' lists of textbooks and found 22 suitable books. After compiling a standard list of questions on intravenous therapy, we read each book to find out to what extent it delivered the answers, and listed the information obtained. RESULTS Only 13 books answered more than half of the questions. The information varied considerably. Suggested quantities of daily fluid, sodium and potassium requirements varied hugely. CONCLUSIONS Information provided in standard textbooks to guide fluid prescription is scant and variable. This could be a cogent reason why junior doctors prescribe postoperative fluids badly: the information in textbooks is inadequate and varies from book to book. The reasons for the poor coverage are not clear. Perhaps other common topics that are often poorly managed are also badly addressed by standard books.