As in humans, diseases in animals may lead to characteristic changes of the voice. In particular, multiparametric frequency, time analysis, as well as the amount of nonlinear phenomena (frequency jumps, subharmonics, biphonation, chaos) provide information about the well‐being of an animal and the progress of a disease. Vocalization of domestic animals (dogs and cats) in a university hospital and of a macaque species in a zoological garden have been recorded. First results show that diseases lead typically to shortened call length and decreasing frequency modulation in the cat. Using narrow‐band spectrogram subharmonics, biphonation, frequency jumps, and deterministic chaos are identified during the recuperation process of a cat with craniocerebellar trauma. The same nonlinear phenomena appear in several dogs with dysphonia following exhaustion of the voice and in a Japanese macaque infant with an unidentified systemic disorder. The ratio of nonlinear phenomena during systemic disorders of an animal shows a species‐specific pattern. There was an increase mostly of frequency jumps in the macaque infant, of frequency jumps and chaos in the dog, and of chaos and subharmonics in the cat vocalization. [Work supported by NaFoeG, Humboldt‐University Berlin.]