Dispersed pancreatic islet cells from rats were cultured overnight in the presence of macroporous gelatin microcarriers. The cells attached to the microcarriers were then incubated for 90 min in the absence or presence of 15.0 mM D-glucose and/or 1.25 mM theophylline. The release of insulin during incubation was about three times higher in the simultaneous presence of these two secretagogues than in their absence. This procedure could thus be used for the immobilization of pancreatic islet cells with preserved secretory potential.