A transgenic mouse having somatic and germ cells in which at least one allele of an endogenous interleukin-1.beta. converting enzyme (ICE) gene is functionally disrupted is provided. The mouse may be heterozygous or, more preferably, homozygous for the ICE gene disruption. In homozygous mice, secretion of mature interleukin-1.beta. and interleukin-1.alpha. is substantially reduced relative to non-mutant mice. The mice of the invention can be used as positive controls to evaluate the efficacy of ICE inhibitors and to identify disease conditions that can be treated with ICE inhibitors. A transgenic mouse having functionally disrupted endogenous ICE genes but which has been reconstituted with a human ICE gene is also provided. This mouse can be used to identify agents that inhibit human ICE in vivo. Nucleic acid constructs for functionally disrupting an endogenous ICE gene in a host cell, recombinant vectors including the nucleic acid construct, and host cells into which the nucleic acid construct has been introduced are also encompassed by the invention.