Measurements of the composition of the condensed phases derived from the sinter feed to a commercial lead blast furnace are presented. No significant reaction was detected at a level in the furnace above about 3 m from the tuyeres, at which the measured temperature was about 800 °C. The reaction zone was predominantly in a region 1 m to 2 m above the tuyeres accompanied by fusion and phase separation. Results do not agree with the predictions of a mathematical model. Some additional measurements of gas composition, temperature, and pressure are also given. Oxygen enrichment of the blast air has resulted in more uniform temperature and pressure profiles in the furnace. The principal phases present in the sinter feed are silicates and ferrites. As the sinter descends, the lead silicates and ferrites react to form lead metal, hardystonite, and wustite.