Very long baseline interferometry (VLBI) observations collected primarily under projects POLARIS (Polar-Motion Analysis by Radio Interferometric Surveying) and IRIS (International Radio Interferometric Surveying) since 1980 have been used to derive polar motion and UT1 time series. The typical 24-hour observing sessions using the multistation North America-Europe network yield estimates of the X and Y components of the pole with uncertainties of 1-2 milliseconds of arc (mas) and UT1 with uncertainties of 0.05-0.1 ms of time. (Preliminary experimental results indicate that UT1 can be tracked by a single VLBI interferometer to the 0.1-ms level in observing periods of about 1 hour.) The same observations have been used to estimate the relative rates of motion of the North American and European tectonic plates and investigate possible regional deformations of the North American plate, with uncertainties of a few millimeters per year; check the accuracy of the adopted nutation series to the millisecond of arc level; estimate earth tide Love numbers for each observatory site with uncertainties of about 1% in h and 25% in l; and determine the coordinates of 20 radio sources to a few milliseconds of arc. Temporal variations in the apparent positions of the radio sources caused by relativistic deflections of the radio signals in the solar gravitational field have been used to estimate the relativistic deflection parameter &ggr;, yielding a value of 1.000¿0.003.