The deposition of suspended iron oxide in boiling water at atmospheric pressure on a heated Zircaloy surface has been studied. The effects of various factors, including heat flux of the heated surface, concentration of iron oxide, and flow rate of boiling water, on the deposition rate during the initial period have been investigated. A model based on the microlayer evaporation and drying out phenomena that occur in the nucleate boiling bubble is proposed for an interpretation of the deposition rate. Close agreement is obtained between calculations using that model and the experimental results.