This article reviews current efforts and plans for gravitational-wave detection, the gravitational-wave sources that might be detected, and the information that the detectors might extract from the observed waves. Special attention is paid to (i) the LIGO/VIRGO network of earth-based, kilometer-scale laser interferometers, which is now under construction and will operate in the high-frequency band (1 to 10⁴ Hz), and (ii) a proposed 5-million-kilometer-long Laser Interferometer Space Antenna (LISA), which would fly in heliocentric orbit and operate in the low-frequency band (10⁻⁴ to 1 Hz). LISA would extend the LIGO/VIRGO studies of stellar-mass (M∼2 to 300 M_⊙) black holes into the domain of the massive black holes (M∼1000 to 10⁸M_⊙) that inhabit galactic nuclei and quasars.