The hygienic consequence of a lamb carcass cooling process can be assessed by evaluating the product's time-temperature history at a site within the carcass cavity adjacent to the 5th and 6th lumbar vertebrae. From these data, a numerical value, the process hygiene index, is generated which reflects the amount of potential bacterial growth the process allows and is proposed as an alternative quality assurance tool for assessing lamb cooling processes. Two hygienically acceptable lamb cooling processes, one producing carcasses destined for freezing and the other producing carcasses destined for chilled processing, were monitored. Acceptable cooling processes can be conveniently described in terms of a three class sampling plan where the maximum acceptable value (M) is the highest value obtained and the target value (m) is determined as the 80th percentile value of the pooled data from acceptable runs. The number (c), the proportion of sample values that may lie between (m) and (M), is determined from the acceptable run with the highest sample values. For the process yielding carcasses destined for freezing M = 15, m = 14 and c = 20% while for that producing carcasses for chilled processing M = 9, m = 6 and c = 60%. For both processes a minimum of five samples was tested per process run. Based on these values, provisional processing guidelines for the hygienic cooling of lamb carcasses are suggested.