Abstract 1. 1. Blood samples were obtained from cattle and buffaloes over extended periods of time by remote controlled methods at 4-hourly intervals. 2. 2. Initial handling of the animals and deliberate exposure to stress at the end of the experimental times resulted in increased plasma concentrations of a number of variables. 3. 3. Between initial handling and applied stress, the concentration of all variables investigated showed little change and no evidence of rhythms. 4. 4. The results obtained reflect true plasma composition of free ranging cattle and buffaloes at rest.