Aerated concrete is a relatively homogeneous material as compared with conventional concrete since it is devoid of the coarse aggregate phase, yet it exhibits vast variation in its properties. Most of the investigations in the past have been confined to autoclaved products. This paper reports the results of a systematic study conducted to ascertain the influence of the lime–cement ratio, fly ash as a partial/complete replacement of sand, the particle size of sand and the dosage of aerating agent on the density and compressive strength of moist-cured and autoclaved aerated concrete. This study establishes that from the viewpoint of density reduction, fly ash can play a pivotal role in aerated concrete, without much compromise on strength. An increased lime–cement ratio is observed to affect adversely the strength, whereas a reduction in the particle size of the sand below a certain level is not justified in the case of non-autoclaved aerated concrete.