The dispersion process of laponite clay powder in water was investigated using light scattering. The complete dispersion process takes about 12 h. Laponite solutions were characterized in salt-free water and in 10(-3) M NaCl using static and dynamic light scattering, which shows that laponite has a large size polydispersity if it is assumed that it disperses into individual particles. Alternatively, if it is assumed that laponite particles are monodisperse, the results imply that it disperses into a distribution of individual particles and small oligomers. Laponite solutions also contain a small fraction of very large aggregates which dominate the scattering at small scattering wave vectors, but which can be removed by filtration. If the ionic strength is increased, the clay particles aggregate with a rate that strongly increases with increasing ionic strength. At ionic strength above 2 x 10(-3) M the aggregation may interfere with the dispersion process.