This report constitutes principally an assessment of the impact of natural gas on the treatment of the Port Pirie slag dumps for recovery of zinc, and an estimate of the amount of gas which would be consumed(a). Subsequent treatment of the slag and other metallurgical uses for natural gas have been mentioned in passing. Leaching was investigated for extracting zinc from slag but no economic process has been devised. On the other hand there are numerous pyrometallurgical processes all of each which depend on the reduction of zinc in the slag to metallic zinc. Electrolysis of molten slag is reported to have been used successfully on a pilot scale to reduce metallic zinc, and the use of metallic iron as reductant has been proposed38(b). Most of the processes however, use a carbonaceous reducing agent in solid, liqiud or gaseous form. Since the thermodynamics of reduction of zinc silicate to metallic zinc by CO or H2 are only favourable at tempreatures above about 1100 degrees celcius ie above the melting point of most slags encountered in practice, the zinc (boiling point 930 degrees celcius) is immediatley volatilised. If the atmosphere above the molten slag is maintained sufficiently reducing. It is possible to condense metallic zinc, 6,45 but generally the zinc vapour re-oxidises to ZnO which is recovered in baghouses. The use of natural gas as the carbonacous reductant in the presently used processes is discussed, most emphasis being placed on the slag-fuming process. This urgent assessment has necessarily been brief, and the estimates made must be taken as approximate only.