Morbidity and mortality of the young calf represent a major cause of economic concern for producers . The objective of the study was to evaluate the performance and immune status of calves reared in the presence or absence of quartz linear heating lamps (CD 3000) and fed calf milk replacer either by bucket or by teat. Mart-purchased Holstein/Friesian calves were approximately 21 days of age at arrival at the research centre. The calves were allocated randomly to one of the following four treatments (n = 16 calves per treatment) using a 2 × 2 factorial design; 1). Teat fed + quartz linear lamp (QLL) (2). Bucket fed + QLL; 3). Teat fed + no QLL and 4). Bucket fed + no QLL. For the 42-day experimental period, 8 groups of 8 calves were penned (2.4 × 10.0 m) on straw in a naturally ventilated Monopitch calf house. A quartz linear heating lamp (3 k output) was positioned in the centre of the individual sheds, 10 feet above the floor of the straw bedded pens for these on QLL treatments, and remained switched on for the duration of the study. The calves received an individual allowance of 25 kg of milk replacer powder offered warm (38°C) by bucket and had ad libitum access to a concentrate ration. Individual disease episodes were determined by the requirement to treat with antibiotics for either enteric disease or respiratory disease. Serum immunoglobulins (IgG1) were measured quantitatively by single radial immunodiffusion standard and calculated via an internal Ig standard (100 mg/L) on days 1, 14 and 28 of the study. Haematological parameters were measured on days 1, 14 and 42 of the study and included red blood cell number, haemoglobin, packed cell volume, mean cell volume and total white cell counts. The data were analysed using a model appropriate to factorial design, with terms for QLL and teat in the main plot. The average temperature and relative humidity of the shed compartments with and without the QLL heating lamps were recorded continuously and were 11.3°C and 81% and 10.5°C and 86%, respectively. There was no significant difference (P > 0.05) between treatments with respect to liveweight gain from day of arrival (day 1) to day 42 of the study. There was no significant interaction between QLL, no QLL, teat fed and bucket fed treatments with respect to serum IgG1 concentrations and haematological parameters throughout the study period (P > 0.05). The incidence of respiratory disease and enteric disease was similar across the treatment groups (P > 0.05). It is concluded that the rearing of calves indoors, in the presence of quartz linear heating lamps, and either fed calf milk replacer by teat or bucket had no beneficial effect on calf health and performance when compared with calves reared in a natural ventilated environment.