An objective method for measuring sperm motion characteristics was developed on an Intellect 100 Quantel Image Analysis System suitable for various image cytometric applications. It provided overall analysis of percent motility (% MS) as well as individual and mean measurements of motion characteristics, including vigor characteristics such as curvilinear velocity (Vc), straight line velocity (Vsl), and trajectory pattern characteristics, that is, progressiveness ratio (PR) and amplitude of lateral head displacement (Alh). Evaluation of the method for reproducibility and accuracy showed reliable measurements of these parameters measured on a minimum of 70 motile sperm, sufficient to describe adequately the sperm population. A study was performed comparing motion characteristics of 30 semen samples falling in a normal range before and after cryopreservation in cryoprotector medium (CM). A mean motility rate of recovery (MRR) of 45% was obtained. Only sperm count and concentration in motile forms among initial semen variables correlated weakly with MRR. Velocity recovery rate (VRR) approached 1 with a marked variability among ejaculates. Distribution profile of Vc was highly modified by freezing in CM: spermatozoa that were initially fast and progressive were the most resistant to cryoaggression. PR and Alh values were little affected by freezing in CM. The tolerance of various samples from a given patient was highly variable for % MS and Alh and less variable for Vc and PR. This illustrates the difficulty in predicting the effect of freezing on motility characteristics and, therefore, of extrapolating from semen variables the ability of frozen-thawed samples to fertilize.