AbstractDNA synthesis was measured during a 30 hour period in stem segments containing a wound — either sterile or inoculated withAgrobacterium tumefaciens— and in control stems ofVicia faba.An identical series of experiments was conducted both on upper, still growing internodes and on lower, mature ones. The incorporation of3H‐thymidine was determined from extracted DNA with a liquid scintillation spectrometer. The results from the two internodes were fairly similar. DNA synthesis was not significantly different in the two types of wounds. It rose above control level at about 10 hours after wounding and reached its peak at about 19 hours. Roughly, this pattern of DNA synthesis seems to correspond to the minimum conditioning and transformation time as found in other plants. However, the decisive factor need not be DNA synthesis, but could be some other process coinciding wi