Qualitative and quantitative evaluation of aerobic and anaerobic faecal flora was determined by a new and easy method. 10 microliter of 12 ten-fold dilutions in saline of samples of faeces were plated on the surface of culture media solidified in wells of sterile virology plexiglass plates (diameter 16 mm; 0.5 ml culture media) and incubated at 37 degrees C for 24 h. The same dilutions and the same plexiglass plates were used under anaerobic conditions for analysis of anaerobic flora (under atmosphere of N2 85%, CO2 10%, H2 5%, negative pressure, at 37 degrees C for 48 h). The analysis was performed on 35 healthy breast-fed newborn infants, 1--6 days old. After birth, the meconium in sterile; already at 25 h of life some bacterial species (Lactobacilli, Bifidobacteria, Bacteroides) show the maximal concentration in faeces and do not grow afterwards; other bacterial species (Coliforms, aerobic and anaerobic Streptococci) increase gradually during the first week of life. This method gives the same results as the conventional techniques (i.e. Petri dishes), but in an easier and quicker way; therefore it seems useful in clinical practice.