Exhibit 99.31 MBNA MASTER CREDIT CARD TRUST II SERIES 1999-B KEY PERFORMANCE FACTORS May 31, 2001 Expected B Maturity 3/16/09 Blended Coupon 5.9788% Excess Protection Level 3 Month Average 7.68% May, 2001 7.52% April, 2001 7.45% March, 2001 8.08% Cash Yield19.67% Investor Charge Offs 5.45% Base Rate 6.69% Over 30 Day Delinquency 4.84% Seller's Interest 8.52% Total Payment Rate14.20% Total Principal Balance$58,203,705,030.43 Investor Participation Amount$750,000,000.00 Seller Participation Amount$4,958,014,468.94