Thidiazuron (N-phenyl-N-1,2,3- thiadiazol-5-ylurea; TDZ) induces high frequency of shootlet multiplication in sugarcane cultures. Shootlets taken from aseptic cultures established from apical domes were kept on media supplemented with various concentrations of TDZ. After 24 days, level of TDZ as low as 1x10^-9 M showed higher number of shootlets compared to control.  Sub culturing of these TDZ-treated shootlets on media with no TDZ showed continued high shootlet proliferation.  The data suggests that TDZ remains effective for several weeks after its application. Sustained TDZ effects at such low concentrations are uncommon.  Protein profiles using SDS-PAGE showed that six new proteins of M.W. 131.8, 125.9, 117.5, 89.1, 74.1 and 70.7 kD appear in response to TDZ.  Also, DNA from proliferating TDZ-treated shootlets was extracted and amplified against random decamer primers.  An RAPD fragment of 200 bp amplified against primer 5`-AGCCAGCGAA-3` (50AO16) disappeared in 10^-7 M TDZ, while three others of size 550, 360, and 320 bp amplified against primer 5`-GGACTGGAGT-3` (60BO4) were absent in all treatments, but present in control in sugarcane var. CoH-92.  An RAPD product of 950 bp amplified by primer 5`-AATCGGGCTG-3` (10A04) and another of the same size amplified by primer 5`-GTAGACCCGT-3` (90B11) were observed in all treatments except control.  In var. Co-7717, RAPD fragments of 1200 bp amplified against primer 5`-TCGGCGATAG-3` (40AO10); of size 1150, 1000 bp and 900 bp against primer 5`-CTGCTGGGAC-3` (80B10) and of size 500 bp against primer 5`-GTAGACCCGT-3` (90B11) were observed in all treatments but not in control. Alterations in DNA amplification products are a new and hitherto unsuspected effect of TDZ.