OBJECTIVE--To compare (1) the reliability of two expensive and two inexpensive measuring instruments, suitable for use in the community and (2) the reliability of experienced compared with inexperienced observers. DESIGN--(1) Ten children aged 5-12 years were each measured three times blindly, and in random order, by two experienced observers using four different portable instruments. (2) Four groups of four children aged 5-11 years were each measured three times blindly, and in random order by four experienced and one inexperienced measurer, using two different portable instruments. MAIN OUTCOME MEASURES--The precision of height measurements made by different observers using different instruments, expressed in each case as the standard deviation of a single height measurement (SDshm). RESULTS--(1) No significant difference in precision was found between instruments, SDshm ranging from 0.22-0.34 cm. The two observers using apparently the same technique, did however record significantly different absolute heights. (2) No significant difference in precision was found between experienced and inexperienced observers. CONCLUSION--Inexpensive height measuring equipment, once accurately installed, is no less reliable than the most expensive. Inexperienced observers can, with care, measure as reliably as those with long experience. Every effort should be made, however, to ensure that the progress of individual children is monitored not only by the same observer, but on a long term basis.