  The last decade has shown a considerable development of gravitational lensing
for cosmology because it probes the amount and the nature of dark matter, and
provides information on the density parameter $\Omega$, the cosmological
constant $\Lambda$ and the Hubble constant $H_{o}$. Therefore, gravitational
lensing can constrain the cosmological scenario which gave birth to the
Universe as it appears today. The ongoing programs and future projects which
are developing now all over the world show that gravitational lensing is
considered as a major cosmological tool for the coming years as well. In this
review, we summarize some of the most recent advances in the fields relevant
for the dark matter issue. We will focus on the microlensing, the arc(let)s and
the weak lensing studies. The possibility to check the existence of a non-zero
$\Lambda$ is presented elsewhere.
