The concentration of beta-carotene analyzed in blood serum of 30 healthy men and women aged 17-50 years by the method of HPLC in May-June 1990 was in range 3.3-29.5 and in average 12.0 +/- 1.2 micrograms/100 ml. Concentration of carotene determined by Bessay's spectrophotometric method as sum of carotenoids composed 58.0-215.0 and in average 120.5 +/- 7.5 micrograms/100 ml. This level of carotenoids is higher by 10 times than level of beta-carotene detected by HPLC. But the levels of carotenes in blood serum detected by two methods are in positive correlation (r = 0.8). Single intake by volunteers 25 mg of synthetic beta-carotene in three different forms (as cyclodextrin derivation, or 30% microcrystalic suspension in vegetable oil, or 10% water-soluble form produced by Hoffman-La Roche company) caused increasing of beta-carotene concentration in serum with maximum within 24-48 hours. Bioavailability of cyclodextrin derivation of beta-carotene, determined by absolute increasing of beta-carotene concentration in serum, was lowest than that of other forms. Bioavailability of beta-carotene as 30% microcrystalic suspension in vegetable oil or 10% water-soluble form was practically the same. Intake of beta-carotene did not effect on level of retinol in serum which was in normal range.