A kinematic formalism for the Eulerian and Lagrangian analysis of drifter data is developed for homogeneous, isotropic, two-dimensional flows which exhibit a preferred sense of rotation. Principal results include a new measure of rotation h*, defined from orthogonal velocity components, which is related to the covariance of horizontal divergence and rate of change of vorticity. An analogous Lagrangian correlation hL may indicate a rotational sense opposite to h* due to the preferential sampling by drifters of regions of previous net convergence which are regions of cyclonic vorticity for quasigeostrophic motions. These kinetic results are illustrated by an analysis of 197 iceberg trajectories from the Labrador shelf, which do indeed show opposite rotational senses for h* and hL.