The solar wind density begins to become enhanced at the same time that azimuthal flow removes material from compressions built up by stream-stream interaction. This lateral flow delays the formation of a shock and the resulting onset of enhancement in the magnetic field. The density increases typically six hours before the field and velocity increase. Density enhancements in the ISEE 3 data are identified here by use of an algorithm that is based on both the three-hour averages of the density and daily averages of the density. In the ISEE 3 data from the first twenty weeks following launch on August 12, 1978, 25 density enhancements were picked out by the algorithm. The times at which these enhancements started were used for superposed epoch analyses. The variables examined were the geomagnetic activity index (Kp), the ring current index (Dst), the field magnitude, the absolute value of the north-south field component, (BN), the solar wind velocity and the composite standard deviation of the field components. These variables became enhanced six or more hours after the time when the density enhancement condition was first satisfied. The distribution of current sheet crossings showed no systematic behavior in a superposed epoch treatment. The results of the superposed epoch analyses indicate that density enhancements can be used to anticipate the occurrence of enhanced geomagnetic activity.