Abstract: A device for particle agglutination analysis and a method for its use. The device includes means forming a longitudinally extending channel, an opening communicating from the exterior of the device to a first end of the channel, a reservoir communicating with the second end of the channel, and a vent opening communicating from the reservoir to the exterior of the apparatus. The channel has a sufficiently large cross section and the vent is positioned such that, when the channel is in a vertical position, a given amount of fluid, introduced through the opening into the channel will flow by gravity through the channel and into the reservoir, filling the channel to a desired height and the reservoir to the same height without flowing through the vent, while air escapes through the vent. Gravity causes sufficient movement of the particles so that agglutination may occur.