Giardia lamblia is a flagellated protozoan of great medical
and biological importance. It is the causative agent of giardiasis, one
of the most prevalent diarrheal disease both in developed and
third-world countries. Morphological studies have shown that G.
lamblia does not present structures such as peroxisomes,
mitochondria, and a well-elaborated Golgi complex. In this review,
special emphasis is given to the contribution made by various
microscopic techniques to a better knowledge of the biology of the
protozoan. The application of video microscopy, immunofluorescence
confocal laser scanning microscopy, and several techniques associated
with transmission electron microscopy (thin section, enzyme
cytochemistry, freeze-fracture, deep-etching, fracture-flip) to the
study of the cell surface, peripheral vesicles, endoplasmic
reticulum–Golgi complex system, and of the encystation vesicles
found in trophozoites and during the process of trophozoite-cyst
transformation are discussed.