Subjective memory complaints (SMCs) are common in older people and are often thought to indicate cognitive impairment. We reviewed research on the relationship between SMCs and (a) current cognitive function, (b) risk of future cognitive decline, and (c) depression and personality. SMCs were found to be inconsistently related to current cognitive impairment but were more strongly related to risk of future cognitive decline. However, SMCs were consistently related to depression and some personality traits, e.g. neuroticism. In conclusion, the determinants of SMCs are complex. The utility of SMCs in the diagnosis of pre-dementia states (e.g. mild cognitive impairment) is uncertain and requires further evaluation.