  With its planet detection efficiency reaching a maximum for orbital radii
between 1 and 10 AU, microlensing provides a unique sensitivity to planetary
systems similar to our own around galactic and even extragalactic stars acting
as lenses on observed background stars, and in particular can detect
terrestrial planets in the habitable zone. The absence of planetary signals in
the 1995-1999 PLANET data implies that less than 1/3 of galactic M-dwarfs
harbour jupiters at orbital radii between 1.5 and 4 AU. If a fraction f_p of
stars is surrounded by a planet, annual detections of 15--25 f_p jupiters and
2-3 f_p earths around galactic stars would result from PLANET, a space-based
campaign would yield 1200 f_p jupiters and 30 f_p earths, and a northern
microlensing network could detect 15-35 f_p jupiters and 4-10 f_p saturns
around M31 stars.
