AbstractIn a cross‐over study on 6 healthy volunteers, the serum concentrations and the bioavailability of 16 oral phenoxymethylpenicillin preparations have been compared. The dissolution rates of the tablets and capsules were studied. The preparations included 5 aquous solutions, 7 tablets or capsules, and 4 suspensions. The highest bioavailability was seen with the aquous solutions and the tablets or capsules containing the potassium salt of phenoxymethylpenicillin. Two calcium salt tablet brands showed lower serum mean concentrations and bioavailability than the other, potassium salt, tablets and capsules, but the differences were only statistically significant for one of the calcium salt tablets as compared to the tablet with the highest mean concentrations. The poorer bioavailability of the calcium salt tablets was reflected in longer dissolution times. The suspensions intended for paediatric use were significantly inferior to most of the other preparations. The lowest bioavailability was observed with a suspension containing the poorly soluble benzathine phenoxymethylpenicilli