Experiments are performed in which a large number ( similar to 10(4)) of relaxation oscillators are globally coupled through the concentration of chemicals in the surrounding solution. Each oscillator consists of a microscopic catalyst- loaded particle that displays oscillations in the concentrations of chemical species when suspended in catalyst- free Belousov- Zhabotinsky ( BZ) reaction solution. In the absence of stirring, the uncoupled particles display a range of oscillatory frequencies. In the well- stirred system, oscillations appear in the surrounding solution for greater than a critical number density of particles ( n(crit)). There is a growth in the amplitude of oscillations with increasing n, accompanied by a slight increase or no change in frequency. A model is proposed to account for the behavior, in which the transfer of activator and inhibitor to and from the bulk medium is considered for each particle. We demonstrate that the appearance and subsequent growth in the amplitude of oscillations may be associated with partial synchronization of the oscillators.