The chromatographic behavior of beta-lactoglobulins when eluted in hydrophobic interaction chromatography systems is studied. By modifying some factors, such as pH and temperature, the relationship between shape of the chromatographic peak and protein structure is shown. At pH 4.5 and low temperature multiple peaks for beta-LG A and beta-LG B are observed and assigned to aggregates. The effects of other parameters, besides pH and temperature, such as volume and concentration of injected sample, contact time between protein and stationary and/or mobile phases, and nature and concentration of mobile phase upon aggregation are studied. Comparison of the chromatographic behavior of both variants of beta-lactoglobulin is made.