The term "welfare" refers to the state of an individual in relation to its environment, and this can be measured. Both failure to cope with the environment and difficulty in coping are indicators of poor welfare. Suffering and poor welfare often occur together, but welfare can be poor without suffering and welfare should not be defined solely in terms of subjective experiences. The situations that result in poor welfare are reviewed in this study with special reference to those in which an individual lacks control over interactions with its environment. The indicators of poor welfare include the following: reduced life expectancy, impaired growth, impaired reproduction, body damage, disease, immunosuppression, adrenal activity, behavior anomalies, and self-narcotization. The uses of measures of responsiveness, stereotypies, and animal preferences in welfare assessment are discussed. The need to make direct measurement of poor welfare as well as to use sophisticated studies of animal preferences is emphasized.