The effect that the duration of cold stress in reference to how long after the chickens were immunized was studied in three lines of chickens. Two of the lines were bred for either high or low antibody responses and the control was a random-breed line. The chicks were restricted fed at 80% of ad libitum intake levels. Chicks that were 26 days old were exposed to 10ºC temperatures for 0, 2 or 7 days. The chicks were immunized with keyhole limpet homocyanin (KLH) –1, +1, +3, +5 or +7 days following the cold stress. The cellular immunity of the chicks was measured by in vitro lymphocyte proliferation in response to concanavalin A (conA) and KLH. Phagocytosis was measured also measured. The exposure to cold stress negatively affected the body weight gain of the chickens. Exposure to cold stress for seven days significantly enhanced cellular immunity to conA. However, exposure to cold stress for two days had a varying effect on the lymphocyte proliferation in response to conA and was dependent on the chickens’ genetics and the timing of the immunization. The lymphocyte proliferation in response to KLH was enhanced in hens that underwent two days of cold stress 28 days after they were immunized. Cold stress did not affect the antibody response to KLH, but it delayed the mitogen response to conA. The high antibody line of chickens had a higher response to KLH than the other lines. The lymphocyte response to conA was lower in chickens bred to have lower antibody responses. The response of the immune system (phagocytosis) to cold stress was immediate. However, this response was quite variable and the response was not affected by whether they were chickens bred to have high or low antibody responses. When the chickens underwent cold stress for a longer amount of time, the cellular adaptive response, and the humoral immune response were affected to a small degree. There was not an interaction between genetic lines and treatments, which suggests that the genetics that affected the degree of the specific immune response. Overall, when a chicken is feed-restricted and undergoes stress at the same time, their cellular immunity is more sensitive than their humoral immunity. As well, the negative correlation between body weight gains and cellular immunity implies that by enhancing one trait results in the impairment of the other.