A digital computer program has been developed to calculate plumb-line deflections from gravity data. A region of 1,200 X 1,200 km for which free air anomalies were available was subdivided into units of 50 X 50 km. With n denoting the number of points per unit, each unit was represented by one gravity anomaly calculated as an average in cases where 0<=6 and where n > 50. For 6<=n<=50 the integral mean, obtained from a fitted surface of second order in two variables, was used. W eighting functions were derived for and calculations were done in the rectangular plane coordinate system. For units with sufficient points for surface fitting, the contributions to the deflection components at the centre of the unit from within the unit itself were computed first, and then the effect of the outer region was added. The contributions from the outer region were obtained as the sum of the products of gravity anomalies and weighting coefficients over all units. The computations were repeated with three different origins in order to analyse the effect of the change in the number of points and the point distribution within the 50 X 50 km units. This analysis shows thatnon-uniformpoint distribution may seriously distort the fitted surface, giving erroneous values for the horizontal gradients and hence for the contribution to the deflection components at the centre from within the unit element. The program solves for the gravimetric deflections relative to the origin. To make the two sets of deflections comparable it was necessary to transform the astro-geodetic deflections from Clarke's spheroid to the International Ellipsoid and add a constant term to ail gravimetric deflections. This constant term, representing the effect from beyond the region of integration, is the difference between the astro-geodetic and gravimetric deflections at the origin. A visual comparison of the plotted deflections shows generally good agreement both in direction and in magnitude, indicating that the choice of weighting function, grid distance, and order of fitted surface was suitable. The accuracy of the astro-geodetic and gravimetric deflections is estimated at ± 1 and ± 2 seconds of arc respectively.