PurposeWhile the momentum anomaly is prevalent in South Africa, few have examined the reasons influencing it. This study examines whether momentum profits vary through time and are affected by the state of the market and market volatility between 1998 and 2019.Design/methodology/approachThe authors consider combinations of portfolio construction, such as the lookback period, weighting scheme, measure of volatility and the volatility window period. They further examine the interaction of momentum with sentiment, default risk and semi-deviation as a measure of risk, as a means of testing whether behavioural factors have significant influence.FindingsThe results generally show that neither volatility nor market state has explanatory power on momentum profits.Originality/valueThese results make the momentum anomaly in South Africa an even greater mystery than before as they do not conform to the existing literature from developed economies. The authors do, however, find that default risk is a significant predictor of momentum profits, which is a useful additional factor for those fund managers who utilise momentum strategies. This implies that a fundamental factor, default risk, is a potential explanation for the market-related momentum anomaly.