COLLOID fluid therapy is indicated to treat hypovolaemia and aid the maintenance of plasma volume and intravascular colloid osmotic pressure. The numerous types, preparations and concentrations of colloid solutions available all have varying indications, pharmacokinetics and pharmacodynamics. Selection of a particular product should be based on a sound understanding of these individual characteristics, including their benefits, limitations and side effects. This article describes the properties of commonly used colloid solutions and their indications. Part 1, published in January 2008 (In Practice, volume 30, pp 16-19), discussed patient assessment and the principles of fluid therapy in small animals. Part 2, published in the last issue (in Practice, February 2008, volume 30, pp 85-91), reviewed crystalloid solutions.