Previous studies indicate that porosity in dental microfill composite restoratives reduces the clinical qualities of this group of materials. Porosity may decrease the optical quality of restorations and is probably a strong factor in reducing wear resistance of Class 1 fillings. In view of possibly eliminating this disturbing factor it was the purpose of the present work to study the effect of variables in the clinical technique on porosity. Initially it was found that filling by spatula as well as paste-paste mixing of non-porous microfill materials caused high porosity, and that the visible light curing microfill brands studied were pore-free as delivered by manufacturers. Consequently only this type of material was studied in detail and only when applied by syringing technique. Poor adaptation of composite to tube inside and to cavity walls as well as too small diameter of the tube tip were found to be factors greatly adding to porosity. In cylindrical cavities, 3 mm in diameter and 2 mm deep, porosity could be consistently reduced to zero by wetting the inside of the tube as well as the cavity walls by a drop of visible light curing monomer and by use of tube with a tip opening of 1.0 mm. Similar positive results were obtained for simulated Class 1 fillings. No adverse effects of this technique were found.