In this research the behaviour of an auxotrophic strain of E. coli in the presence of different concentrations of thymine in a synthetic growth medium has been determined. Experimental growth curves have shown that at low concentrations of thymine (> 0.05 $\mu g/ml$) the bacteria underwent the thymineless death, although the “death rate” of the cells was in this case considerably reduced. At thymine concentrations between 0.05 and 0.12 $\mu g/ml$, the number of viable cells remained constant for several hours. Still higher concentrations of thymine allowed cell division to proceed, although with considerably longer generation times than those typical of normal growth.