The present study was conducted to investigate the effects of probiotics on the live weight, live weight gain, feed consumption, feed efficiency and health condition of calves. Nineteen Holstein calves, divided into 2 similiar groups in terms of age, sex and live weight, were used in the trial. The first group of calves were given a probiotic at 20 g/day during the first 2 weeks and 40 g/day in the following weeks, via milk during the first 3 months and later on via drinking water. The other group received no probiotic. Both groups were started in the second week on the same concentrate and good quality alfalfa hay ad libitum, in addition to milk. The probiotic used was a commercial preparation containing Saccharomyces cerevisiae, Lactobacillus acidophilus, Bifidobacterium bifidum, Streptococcus termophilus and Aspergillus niger. Live weight at the end of the experiment, average daily live weight gain, average daily concentrate and (concentrate + hay) intake, feed efficiency ratio calculated as (concentrate + hay) / live weight gain for the no probiotic and probiotic groups were 145.80 +/- 2.28 and 152.00 +/- 3.97 kg, 631.6 +/- 14.7 and 681.6 +/- 15.5 g: 1.727 +/- 0.05 and 1.705 +/- 0.06 kg; 2.403 +/- 0.067 and 2.309 +/- 0.071 kg; 3.80 +/- 0.07 and 3.38 +/- 0.08, respectively. No significant differences were observed between the groups, except for the daily live weight gain (P < 0.05) and feed efficiency ratio (P < 0.01). Diarrhea was observed in the control group, while there were no health problems in the probiotic group.