Single-chain single crystals of gutta-percha have been observed by tra
nsmission electron microscopy of atomizer-sprayed particles deposited
from a very dilute solution in chloroform onto a carbon film which had
a filter paper wetted with ethanol in contact with its under side. Se
lected-area electron diffraction patterns of crystals having no defini
te crystal profiles showed that the crystals were of the low-melting c
rystalline form and that the chain segments in the single crystals wer
e standing up from the substrate during crystallization. In cases of s
ingle crystals showing sharply defined crystal profiles, electron diff
raction patterns showed that they were neither of the low-melting form
nor the high-melting form. The structure of this new crystalline modi
fication needs further studies.