Information about all produced light building materials, their production, properties and utilization in building work. In the theory of Lightweight Building Materials, the classification of light building materials is involved and the general basic properties etc. Into the second part - the technology of lightweight aggregates, the knowledge of natural cellular aggregates and of concrete produced from them is involved, further untreated industrial wastes (for instance cinder, fly ash from power plants etc.), further treated industrial wastes used as porous aggregates (slag, fly ash aggloporite), synthetically produced porous aggregates and the classification of them (for instance ceramsit, expandit, perlit, vermikulit etc.). Between these materials belong even light organic aggregates( sawdust, wood shavings, light aggregates from plastics) and mineral fibres. The third part is the technology of -cellular concrete, beginning with the classification of cellular concrete, the used raw materials, processing, shaping, autoclaving etc. till to the individual products and their utilization.