When making use of potentiometric micro-analytical methods in fluoride determination, only a portion of the lantanium fluoride (LaF) crystal of the fluoride electrode is employed. Although there is no difference in sensitivity when using either the total surface or a part of the surface of the LaF crystal, there are advantages in using the total surface of the crystal. For the purpose of utilizing these advantages to a maximum, a semi-micro-analytical method of fluoride determination was developed. A perspex electrode container with a specimen capacity of 50 microliters was designed and constructed in order to bring the total surface of the LaF crystal into contact with the testing solution. Due to the inexpensive and simple design of the containers there are practically no restrictions on the number that could be employed. The solution obtained from a single enamel biopsy could be used for at least two or three analyses. The results obtained by employing the technique described, showed that the method is precise and accurate. The semi-microanalytical method offers an alternative to the micro-analytical method of fluoride determination in enamel biopsies.