The validity of the use of the scales of charr (Salvelinus willughbii Günther) in Windermere for the calculation of age and growth has been investigated. From reared fish it was established that an annulus was formed on the scales each year. The body length/scale length relationship was isometric in fish over 95 mm in length; for lengths smaller than 95 mm corrections for allometry have been calculated. Length frequencies found by back-calculations to the first annulus show differences between charr spawning in the spring and those spawning in the autumn. The length frequencies of spring spawners are bimodal, those of autumn spawners unimodal. Initial formation of scales was related to length of fry, and it is suggested that the bimodal distribution of the spring spawners is caused by some of the spring spawned fry not having grown to a sufficient length to lay down scales before their first winter of life; the first annulus on their scales is therefore formed during the second winter of life and back-calculation to this annulus gives their length at age 2 years, thus missing the length at age 1 year. This “missing first year” is a phenomenon that occurs on some, but not all, spring spawners, and on none of the autumn spawners. Tagging experiments showed that in older fish, aged 5 years and more, annuli could sometimes be missing due to the erosion of the edge of scale and slow growth of the fish. It is concluded that the scales of the charr in Windermere are satisfactory for the calculation of age and growth up to the age of 5 years, provided that the possibility of a missing annulus on the scales of some fish in the first year of life, the “missing first year”, is recognized. A note on otoliths is included as an appendix; otoliths were found useful for checking ages determined from scales.