Experiments were conducted in a rotary kiln containing ilmenite particles to study the residence time distribution (RTD) of low-density particles, holdup, and bed depth profile. The variables include feed rate of solids, slope and rotational speed of the kiln, type and size of the tracer, and dam height. Correlations are presented for mean residence time, dispersion number, holdup, and steady-state throughput of solids in terms of the process variables. A simple method is proposed to estimate the dam height that gives rise to a flat profile of solids bed along the length of the kiln. © 1990 The Minerals, Metals & Material Society.