Some companies adopt a new manufacturing revolution called industry 4.0, a number of them are lean companies. Industry 4.0 helps companies become more flexible and could respond to the market change easier. Also, it increases product quality and profitability. A growing number of scientists investigated the influence of integration lean and industry 4.0 on each other over the past years. Thus, this paper identifies major gaps for association linking lean and industry 4.0. To execute the research, 35 papers have been reviewed and a classification scheme for them was developed. In order to make the relationship between lean and industry 4.0 transparent, this paper provides a quantitative and qualitative analysis. The result of the qualitative analysis is presented in 3 separate sections titled as follows: 1. Lean is a basis for industry 4.0, 2. Interaction industry 4.0 and lean and, 3. Industry 4.0 completes lean.