Some 40,000 plantlets of Red Spanish pineapple [Ananas comosus (L. Merr.)] were produced via meristem culture. Of these, approximately 50% were spineless. Some of these spineless plantlets reversed to spiny leaf. However, the percentage of reversion from spineless to spiny was 14.1% and that from spiny to spineless was 32.7%. Of the 2,318 plantlets examined in the laboratory and greenhouse during a 3- to 4-month period, 72.9% of the spiny Red Spanish pineapple remained spiny and 85.8% of the spineless remained spineless. One year after field planting, the spineless Red Spanish remained largely spineless and initiated flowering and fruit settings the same as the spiny ones. The standard medium for in vitro propagation of Red Spanish pineapple was improved by supplementing Murashige and Skoog's basic formula (MS) with 0.1 mg/L, 2,4- dichlorophenoxyacetic acid (2,4-D) + 0.5 mg/L benzyl adenine (BA). The callus formation was improved by adding to the same MS formula 10 mg/L BA + 4 mg/L naphtalene acetic acid (NAA). Similarly, shoot differentiation was improved by adding low concentrations of hormone (0.1 mg/L NAA) to the Abo El-Nil and Zettler (AZ) medium.