The long gamma position
Being "long gamma" means holding a position that benefits from large moves in the underlying, regardless of direction. A long straddle (long call + long put at the same strike) is the canonical long gamma position. When the underlying rises, the call gains delta faster than the put loses it (both effects are positive in absolute terms due to gamma). The position becomes directionally long as the underlying rises, and short as it falls. Gamma scalping involves continuously selling that accumulated directional bias — selling the underlying when it rises and buying when it falls — to lock in profits from the moves.
The gamma-theta tradeoff
Long gamma (long options) positions have two opposing forces. Every day that passes without movement, the position loses theta — the daily time value decay of the options. But every significant move in the underlying generates gamma P&L through delta rebalancing. The gamma scalping strategy is profitable if the gamma P&L collected through rebalancing exceeds the theta paid away. This is directly equivalent to asking: was realised volatility greater than implied volatility? If the options were bought at 20% implied vol but the stock moved at 25% realised vol, the strategy is profitable. If the stock barely moved (realised at 12%), the theta decay destroys more value than the gamma scalping recovers.
Implementation in practice
A gamma scalper must decide: how frequently to rebalance? More frequent rebalancing captures more gamma P&L but generates more transaction costs. Less frequent rebalancing leaves more directional risk. The optimal frequency depends on bid-offer spreads in the underlying, the size of the gamma position, and the observed path of the underlying. In highly liquid markets (S&P 500 futures, major currency pairs), intraday rebalancing is feasible. In less liquid underlying, rebalancing only on significant moves (e.g. 1% moves) is more practical. Market makers typically run gamma books across dozens of expiries and strikes simultaneously, netting exposures and scalping the aggregate gamma position.
“Gamma scalping is the practice of systematically harvesting the difference between what the market thought volatility would be (implied) and what it actually was (realised). It is volatility arbitrage made mechanical.”
What this means for you
Gamma scalping is a market-making and institutional strategy, not directly accessible to retail investors. However, understanding it illuminates several important phenomena. First, why options market makers are typically short theta and long gamma by default — they sell options to clients (collecting theta) and hedge the delta, creating long gamma exposure. Second, why the volatility risk premium exists: systematic sellers of options collect theta at the cost of short gamma — they are the counterparty to gamma scalpers. Third, why realised volatility relative to implied volatility is the single most important relationship in options trading. Any informed participant in options markets should have a view on this relationship before putting on positions.